I’ve packed enough outdoor lunches to know that a picnic sandwich has a slightly harder job than the sandwich I make when I’m eating five minutes later at my kitchen counter. It has to survive wrapping, a cooler, a little pressure from everything else in the picnic basket, and sometimes an hour or two before anyone is ready to eat. That is why I usually skip sandwiches that depend on piping-hot cheese, extremely juicy vegetables, or delicate bread. I want sturdy bread, flavorful fillings, and enough moisture to make every bite good without turning the whole thing soggy.

The nice part is that picnic sandwiches do not need to be complicated. Some of the best options are familiar combinations—turkey and cheese, chicken salad, tuna, Caprese, ham and Swiss, Italian deli meats, and peanut butter with fruit preserves—just assembled with travel in mind. Pressed sandwiches are especially useful because sitting for a while actually helps their layers settle together. Muffulettas are famous for that very quality, and picnic collections regularly include other make-ahead favorites such as pan bagnat, Italian subs, chicken salad, egg salad, chickpea sandwiches, wraps, and classic deli combinations. My approach is simple: start with a sandwich people genuinely want to eat, then build it so it still tastes good when the picnic blanket finally comes out.

1. Classic Italian Pressed Picnic Sandwich

An Italian pressed sandwich is one of my first choices when I know lunch will be traveling for a while. I start with ciabatta or another sturdy Italian loaf and layer it with salami, prosciutto or ham, provolone, roasted red peppers, and a modest amount of olive spread or pesto. A few leaves of arugula can go in too, although I keep the vegetables fairly dry. The combination is familiar, savory, and satisfying without needing to be reheated. Pressed Italian sandwiches are a well-established picnic option because the compact loaf is much easier to wrap, carry, and slice than a loosely stacked sandwich.

What really makes this one work is the pressing. Once the loaf is filled, I wrap it tightly and place something heavy over it in the refrigerator for a few hours. The pressure brings the layers together and keeps pieces of pepper, cheese, and meat from sliding out when the sandwich is cut. If I am worried about moisture, I put the cheese directly against the bread and keep wetter ingredients closer to the center. Cut it into smaller rectangles or wedges before leaving home, wrap the pieces individually, and there is very little work left to do at the picnic.

2. Turkey, Cheddar, and Apple Sandwich

Turkey and cheddar is already an easy packed-lunch combination, but thin apple slices give it the crunch that can otherwise disappear after a sandwich has been wrapped for several hours. I like a firm apple rather than a soft variety, and I slice it very thinly so the sandwich stays easy to bite. Sharp cheddar works especially well because its stronger flavor stands up to the turkey and apple. A little Dijon mustard adds enough tang without making the bread wet.

For bread, I would choose sourdough, multigrain, or another fairly sturdy sliced loaf. I put cheddar against both pieces of bread when possible, then arrange turkey and apple between those cheese layers. That small detail creates a useful moisture barrier while also helping hold everything in place. If you are making the sandwiches a few hours ahead, toss or brush the apple slices with just a touch of lemon juice and pat them dry before assembling. You get a sandwich that tastes fresh and crisp even though it was made well before lunch.

3. Chicken Salad and Lettuce Sandwich

Chicken salad is a picnic classic for good reason. It is easy to prepare in advance, filling without being overly heavy, and simple enough for both adults and kids. I make mine with chopped cooked chicken, mayonnaise, a little Dijon, celery, salt, pepper, and either chopped parsley or green onion. Grapes or dried cranberries are optional, but for a sandwich that has to travel, I usually keep the mixture fairly simple and make sure it is creamy rather than runny.

The biggest issue with any salad sandwich is moisture, so I never pile chicken salad directly onto very soft bread hours before serving. A sturdy sandwich roll works well, or I line sliced bread with dry lettuce before adding the chicken. The lettuce acts as a barrier and keeps the bread in much better shape. Chicken salad also needs to stay properly chilled, so this is one of the sandwiches I pack beside ice packs rather than tossing casually into a warm basket. Kept cold, it makes a very dependable picnic lunch.

4. Caprese Pesto Sandwich

A Caprese sandwich gives me the tomato, mozzarella, basil, and pesto combination I want in summer without requiring much kitchen work. I use ciabatta or a crusty roll, fresh mozzarella, ripe tomato, basil leaves, and a thin layer of pesto. A little balsamic glaze is delicious, but I use it sparingly for picnics because too much liquid is the quickest route to soggy bread. Current picnic collections continue to feature Caprese sandwiches because the combination is simple, recognizable, and especially suited to warm-weather eating.

There are two little changes that make it travel better. First, I blot the mozzarella and tomato slices with paper towel before assembling. Second, I arrange mozzarella against the bread so the tomato does not sit directly on it. If the tomatoes are exceptionally juicy, I lightly salt them, let them rest for a few minutes, and blot again. That sounds fussy for such a simple sandwich, but it takes almost no extra time and makes an enormous difference when lunch is not being eaten immediately.

5. Ham, Swiss, and Dijon Sandwich

Some picnic days call for the sandwich nobody has to think twice about, and ham with Swiss is exactly that for me. I layer thinly sliced ham and Swiss cheese on a baguette, ciabatta roll, or sturdy sandwich bread and add a thin coating of Dijon mustard. Pickles are excellent here too, but I drain and pat them dry first. The salty ham, nutty cheese, mustard, and pickle combination has plenty of flavor even when served cold.

I also like this sandwich because there is very little in it that wilts or falls apart. You can make it in the morning, wrap it tightly, and it will still look like a sandwich when you unwrap it later. For a family picnic, I sometimes make one long baguette and slice it into smaller portions rather than building several individual sandwiches. It saves prep time and makes portion sizes flexible for kids and adults.

6. Classic Muffuletta

Few sandwiches make more sense for a picnic than a muffuletta. The traditional combination of Italian meats, cheese, and chopped olive salad is packed into a sturdy round loaf, and unlike delicate sandwiches, it benefits from resting. The flavors of the olive mixture work their way into the bread and meats while the sandwich sits. A classic version can include salami, ham, mortadella, provolone, and an olive salad with pickled vegetables. It is bold, salty, tangy, and substantial enough to serve several people.

I make this one ahead rather than rushing it right before leaving. After filling the loaf, I wrap it firmly and let it rest under light pressure in the refrigerator. Then I cut it into wedges while it is still cold. The sandwich becomes compact enough to hold in one hand, which is exactly what I want when everyone is eating outdoors without a proper table. It is also one of those rare sandwiches where a little time between preparation and eating can improve the final result rather than hurt it.

7. Tuna and Cucumber Sandwich

Tuna sandwiches can travel surprisingly well when the filling is not overloaded with mayonnaise. I combine well-drained tuna with enough mayonnaise to bind it, then add a little Dijon, black pepper, celery, and lemon juice. Thin cucumber slices bring freshness and crunch, especially on a hot day when a very heavy sandwich is not appealing. I prefer seedless cucumber because it generally releases less water.

Before assembling, I pat the cucumber slices dry and put lettuce or cheese between the tuna mixture and bread. Whole-grain bread is particularly good here because its stronger texture can handle the filling better than very soft white bread. Like chicken salad, tuna should remain chilled until it is time to eat, so I always use a well-insulated cooler and ice packs. Prepared and packed properly, this is an easy alternative to deli-meat sandwiches.

8. Turkey Pesto Provolone Sandwich

Turkey, pesto, and provolone gives an ordinary turkey sandwich a little more personality without turning it into something complicated. I spread pesto lightly over a sturdy roll, add provolone, plenty of sliced turkey, and a handful of arugula. Roasted red pepper is another good layer when I have an open jar in the refrigerator, although I always drain it thoroughly before it goes anywhere near the bread.

This is one of my favorite ways to use pesto in a packed sandwich because a small amount gives plenty of flavor. There is no need for a heavy mayonnaise-based sauce on top of it. Provolone also works as a natural barrier between the bread and wetter fillings. Wrap the finished sandwich tightly in parchment followed by foil or a reusable sandwich wrap, and everything stays compact until lunchtime.

9. Roast Beef and Cheddar Sandwich

Roast beef is a good choice when I want a picnic sandwich that feels a little heartier. I pair thinly sliced roast beef with sharp cheddar, arugula, and horseradish mayo or Dijon. The key is keeping the spread thin. Horseradish gives the sandwich plenty of punch, so there is no reason to use a thick layer that will eventually soak into the bread.

A crusty roll is my favorite base because roast beef can be heavier than turkey or ham. The stronger bread keeps its structure even after the sandwich has been wrapped tightly in a cooler. If I am preparing it several hours ahead, I place cheddar on the bottom and top before adding the beef and greens. That protects the bread and gives the sandwich a neat, firm structure when sliced.

10. Peanut Butter and Strawberry Jam Sandwich

There is nothing wrong with bringing a very simple sandwich to a picnic, especially when children are coming along. Peanut butter and jam is one of the easiest sandwiches to transport because there are no delicate vegetables, melted cheeses, or creamy meat fillings to manage. Strawberry jam is my usual choice, but raspberry, grape, or mixed berry works just as well.

My trick for a PB&J that is being made ahead is spreading a thin layer of peanut butter on both slices of bread and keeping the jam in the middle. The peanut butter creates a barrier that slows the jam from soaking into the bread. I also avoid using an enormous amount of jam; too much squeezes out as soon as the sandwich is pressed or bitten. Cut into halves or quarters, these are particularly useful when you need an easy kid-friendly picnic option.

11. Turkey Club Sandwich

A turkey club has enough going on to feel like a complete lunch but still uses ingredients everyone recognizes. I build mine with turkey, crisp bacon, cheddar or Swiss, lettuce, and tomato. Rather than using the traditional three layers of toast when I need it to travel, I simplify the club into a sturdy two-slice sandwich or use a roll. It is much easier to wrap and much less likely to collapse.

Tomato is the ingredient that needs attention. I slice it thin, remove excess seeds if necessary, and blot it well. Cheese goes against one slice of bread, while lettuce protects the other. Bacon adds crunch that survives longer than I expect, especially when it has been cooked properly crisp and cooled before assembling. Keep the mayonnaise light and the sandwich chilled, and the club becomes much more picnic-friendly.

12. Chickpea Salad Sandwich

For a meatless picnic sandwich, mashed chickpea salad is one of the most practical fillings I know. I roughly mash chickpeas and combine them with mayonnaise or Greek yogurt, Dijon, celery, lemon juice, black pepper, and herbs. I intentionally leave some chickpeas chunky rather than turning everything into a smooth paste. That gives the filling texture and makes the sandwich much more satisfying.

Whole-grain bread, pita, or a sturdy roll can all handle this filling. Lettuce is useful both for crunch and for protecting the bread from moisture. I also like that chickpea salad can be prepared the evening before, which takes one more job off the morning picnic list. Keep the finished sandwich cool, just as you would any creamy salad sandwich.

13. Chicken Caesar Wrap

A wrap may not look like the traditional picnic sandwich, but it solves a lot of packing problems. For a chicken Caesar version, I use chopped cooked chicken, crisp romaine, Parmesan, and just enough Caesar dressing to coat everything lightly. Then I roll the mixture firmly in a large flour tortilla. The familiar Caesar flavor makes this easy to serve to a group without wondering whether anyone will find the filling too unusual.

The mistake I avoid is drowning the lettuce in dressing before wrapping it. I use less dressing than I would for a bowl of Caesar salad because the tortilla traps all that moisture. Another option is tossing only the chicken with dressing and leaving the romaine mostly dry. Once rolled, I wrap each sandwich tightly and slice it in half just before packing. The compact shape is especially convenient for picnics where plates are optional.

14. Italian Pinwheel Sandwiches

Pinwheels are one of my favorite options for a picnic with several people because everyone can grab one or two instead of committing to a large sandwich. I spread a flour tortilla lightly with cream cheese or an herbed cream-cheese mixture, then add salami, ham, provolone, and a small amount of lettuce or spinach. Everything gets rolled tightly, chilled, and sliced into neat rounds.

Chilling before slicing is important because it firms up the roll and helps the pinwheels stay together. I also keep the filling relatively thin; overstuffing tortillas is the easiest way to create pinwheels that unravel in the container. Pack them snugly in a single layer or with parchment between layers. They are particularly useful when a picnic includes other finger foods because they fit naturally onto a snack-style spread.

15. Egg Salad and Lettuce Sandwich

Egg salad is another old-fashioned sandwich I still happily bring to a picnic. I make mine with chopped hard-boiled eggs, mayonnaise, a little mustard, salt, pepper, and finely chopped chives or green onion. Celery can add crunch, but I chop it small so the filling stays together instead of dropping out with every bite.

Because egg salad is soft, I prefer bread with a little structure and always add crisp lettuce between the filling and bread. I also keep the salad fairly thick instead of adding extra mayonnaise. This sandwich absolutely belongs in the cooler rather than an unrefrigerated basket. If I know the picnic is going to involve a long drive or hours in the sun without reliable cooling, I choose one of the deli-meat or pressed options instead.

16. Ham and Cheddar Pickle Sandwich

Ham, cheddar, and pickles is a combination I return to whenever I want something uncomplicated but not boring. Sharp cheddar balances salty ham, while dill pickles provide acidity and crunch. I add a little yellow or Dijon mustard and use either sourdough slices or a crusty roll.

The only special preparation is drying the pickles. I place the slices on paper towel for a minute before building the sandwich because pickle brine can quickly soften bread. I also sandwich the pickles between ham and cheese rather than laying them directly on the bread. It is a tiny change, but these little moisture-control habits are what separate a good picnic sandwich from the soggy one nobody wants to finish.

17. Pesto Chicken Mozzarella Sandwich

When I have leftover roasted or grilled chicken, this is one of the easiest ways to turn it into picnic food. I layer sliced chicken with mozzarella, pesto, and roasted red peppers inside ciabatta. Basil or arugula can add a fresh green layer, but the sandwich already has enough flavor without piling in too many ingredients.

This combination is particularly good lightly pressed. I wrap the assembled sandwich tightly and let it rest in the refrigerator for an hour or two so the bread settles around the filling. Mozzarella should be drained and blotted first, and jarred peppers need the same treatment. Those two ingredients can carry more liquid than they appear to, and removing that excess moisture keeps the pesto flavor concentrated rather than watery.

18. Turkey, Brie, and Cranberry Sandwich

Turkey and cranberry does not need to wait for Thanksgiving. It makes a very easy sweet-savory picnic sandwich when paired with Brie or another creamy cheese. I use a thin layer of cranberry spread, sliced turkey, Brie, and a little arugula on a baguette or firm multigrain bread. The result feels more interesting than plain turkey and cheese but still uses completely familiar flavors.

I am conservative with the cranberry sauce because too much can make the sandwich both sweet and slippery. Brie or another cheese layer against the bread helps contain the moisture. If Brie becomes very soft in hot weather, keep this sandwich well chilled and bring it out shortly before eating. For cooler spring or fall picnics, it is an especially nice option.

19. BLT Picnic Sandwich

A BLT is at its best when the bacon is crisp, the lettuce is cold, and the tomato is juicy, which sounds like a recipe for trouble when it has to sit. I still pack them, but I adjust the construction. I cook the bacon until genuinely crisp and cool it completely. I choose firm tomatoes, slice them thinly, lightly salt them, and blot away the moisture before assembling.

I also use sturdier bread than I might at home and spread mayonnaise very thinly. Lettuce can sit against the bread as a protective layer, with tomato closer to the middle and bacon alongside it. If I am traveling a long distance, I sometimes pack the tomato separately and add it at the picnic. For a shorter trip, careful blotting and smart layering are usually enough.

20. Veggie Hummus Wrap

A hummus wrap is an easy vegetarian sandwich when I want something fresh but still sturdy. I spread hummus over a flour tortilla and add shredded carrot, cucumber, bell pepper, spinach, and a little crumbled feta. The vegetables give it plenty of crunch, while hummus provides enough richness that I do not need another sauce.

The important thing is cutting vegetables into thin strips and keeping watery ingredients under control. I remove the soft seed-filled center from cucumber when necessary and pat everything dry. Then I roll the tortilla firmly, folding the sides inward first so nothing falls out. Wraps can be packed very tightly together in a container, making them a good choice when picnic basket space is limited.

21. Chicken Bacon Ranch Wrap

Chicken, bacon, and ranch is a familiar crowd-pleasing combination, and putting it into a tortilla makes it much easier to transport. I use chopped chicken, crisp bacon, shredded lettuce, cheddar, and a small amount of ranch dressing. A flour tortilla holds the mixture together better than soft sandwich bread would.

Again, the dressing needs restraint. I would rather bring a little extra ranch for dipping than saturate the wrap before it spends several hours in a cooler. The chicken can be tossed lightly with ranch while the lettuce stays dry. Roll everything tightly and keep it chilled. It is filling enough for lunch without requiring utensils, which is exactly the kind of picnic recipe I appreciate.

22. Prosciutto, Mozzarella, and Roasted Pepper Sandwich

Prosciutto, mozzarella, and roasted peppers make a simple Italian-style sandwich with enough flavor that very little condiment is necessary. I layer everything on ciabatta with basil, arugula, or a light swipe of pesto. The salty prosciutto does most of the seasoning, while the peppers add sweetness and mozzarella keeps the filling mellow.

This is another sandwich where blotting ingredients matters. Fresh mozzarella and jarred peppers both need to be well drained before they touch the bread. I also like giving the sandwich a short press in the refrigerator. That brings the layers together and makes it easy to cut into smaller picnic portions without the filling sliding in every direction.

23. Classic Turkey and Swiss Sandwich

Sometimes I want the dependable sandwich that I know will disappear without explanation. Turkey and Swiss is that sandwich. I use sliced turkey, Swiss cheese, lettuce, and mustard on multigrain, sourdough, or a roll. Pickles can be added for crunch, but the sandwich does not depend on them.

For family picnics, simplicity can actually be useful. Not everyone wants pesto, olive salad, roasted peppers, or strongly flavored spreads. This one gives picky eaters a straightforward option while still traveling beautifully. Place cheese against the bread, keep lettuce dry, wrap the sandwich tightly, and it can sit happily in the cooler until lunch.

24. Pan Bagnat

Pan bagnat is almost designed for the problem of making a sandwich ahead. This French picnic favorite takes inspiration from Niçoise salad and typically combines tuna, tomatoes, olives, hard-boiled egg, vegetables, herbs, and olive oil in a sturdy round loaf or baguette. Unlike a delicate sandwich that suffers as it sits, pan bagnat is meant to rest so the flavors can mingle.

That does not mean I pour unlimited dressing onto the bread. I still want the loaf flavorful rather than soaked to the point of collapse. Once assembled, I wrap the sandwich tightly and refrigerate it under a little weight. Cut into wedges or portions after it has rested. It is colorful, substantial, and particularly useful when I want one large sandwich to feed several people instead of preparing individual lunches.

25. Turkey and Avocado Wrap

For my last option, I like a turkey and avocado wrap because it feels fresh while remaining simple enough for a picnic. I layer sliced turkey, avocado, lettuce or spinach, cheese, and a little mustard or mayo inside a flour tortilla. The avocado supplies creaminess, so I need much less sauce than I would in a regular turkey sandwich.

Avocado is the ingredient I prepare closest to departure. A little lemon or lime juice slows browning, but I do not use so much that the filling becomes wet. I also place the avocado toward the middle of the wrap rather than directly against the tortilla. Roll it tightly, keep it cold, and eat it earlier in the picnic rather than saving it until the end of a long afternoon.

FAQs About Picnic Sandwiches

What sandwiches are best for a picnic?

I look for sandwiches that are sturdy, flavorful cold or at cool room temperature, and easy to hold. Italian pressed sandwiches, muffulettas, turkey and cheese sandwiches, ham and Swiss, Caprese sandwiches, wraps, pinwheels, pan bagnat, and properly chilled chicken or tuna salad sandwiches all work well. Pressed sandwiches are especially practical because compression helps them stay together during transportation.

How do I keep picnic sandwiches from getting soggy?

My first rule is to control moisture before the sandwich is assembled. Drain roasted peppers, blot tomatoes and fresh mozzarella, pat pickles dry, and avoid excessive dressing. Then create barriers between wet ingredients and bread with cheese, lettuce, deli meat, nut butter, or another relatively dry filling.

Bread matters too. Ciabatta, baguettes, sourdough, rolls, tortillas, and other sturdy options generally handle travel better than very delicate bread. If you are making a sandwich with especially juicy ingredients, consider packing those ingredients separately and adding them shortly before eating.

Can I make picnic sandwiches the night before?

Some are excellent overnight sandwiches. Muffuletta, pan bagnat, and many pressed Italian sandwiches actually benefit from resting because their flavors have time to come together. Wrap them very tightly and refrigerate them until you are ready to pack the cooler.

I am more cautious with sandwiches containing lettuce, cucumber, avocado, or especially juicy tomatoes. Those are usually better prepared the morning of the picnic. You can still prepare individual components the night before so assembly only takes a few minutes.

What bread travels best for picnic sandwiches?

Ciabatta is one of my favorites because it has enough structure to handle fillings without being impossibly hard to bite. Baguettes, sourdough, sturdy rolls, pita, tortillas, and dense multigrain bread are also useful depending on the filling.

Very soft bread can still work for simple combinations such as peanut butter and jam, but it needs protection from moisture. I would not use delicate bread for a heavily dressed Italian sandwich or anything containing several juicy vegetables.

How should I wrap sandwiches for a picnic?

I usually start with parchment or waxed paper because it keeps the sandwich compact and makes it easier to hold while eating. For sandwiches that need especially secure wrapping, I add foil or place the wrapped sandwiches inside a reusable container.

Pressed sandwiches can be wrapped as one large loaf and sliced before leaving home. Pinwheels and smaller sandwiches are easiest to pack in containers where they fit fairly snugly, so they cannot tumble around and unravel.

Which picnic sandwiches should be kept cold?

Sandwiches containing chicken salad, tuna salad, egg salad, dairy-based dressings, cooked chicken, deli meats, and many cheeses should be treated as perishable and kept properly chilled. I pack them in an insulated cooler with enough ice or frozen gel packs and leave them there until we are ready to eat.

For me, food safety is more important than forcing a particular sandwich to fit the picnic plan. If I cannot keep the food reliably cold, I choose a simpler option that is better suited to the situation rather than letting a mayonnaise-based chicken or egg filling sit in warm weather.

How far ahead can I prepare a pressed picnic sandwich?

A few hours is enough for most pressed sandwiches, while sturdy styles such as muffuletta and pan bagnat are commonly prepared well ahead so their flavors can develop. I wrap the sandwich tightly, refrigerate it, and place a heavy pan or another appropriate weight over it.

The exact timing matters less than the ingredients. Dry cured meats, firm cheese, olive spreads, and well-drained roasted vegetables handle resting beautifully. A loaf stuffed with watery cucumber, undrained mozzarella, and heavily dressed greens will deteriorate much faster.

What are the easiest vegetarian picnic sandwiches?

I would start with a Caprese pesto sandwich, chickpea salad sandwich, veggie hummus wrap, or a simple cheese-and-vegetable sandwich. These use ingredients that are easy to find and do not require creating an elaborate meat substitute just to make the sandwich feel substantial.

The trick with vegetarian sandwiches is texture. Pair something creamy, such as hummus, mozzarella, mashed chickpeas, or cheese, with something crisp like carrots, peppers, lettuce, cucumber, or pickles. That contrast keeps a meatless sandwich from feeling flat.

What sandwiches work best for kids at a picnic?

Peanut butter and jam is an obvious favorite when nut allergies are not a concern. Turkey and cheese, ham and cheddar, simple chicken sandwiches, and mild pinwheels are also easy options. I keep strong mustard, olives, spicy peppers, and heavily seasoned spreads off the children’s sandwiches unless I already know they enjoy them.

I also make portions smaller. A huge ciabatta sandwich can be frustrating for a child to hold, whereas quarters, small rolls, or pinwheels are much easier to manage while sitting on a picnic blanket.

What should I avoid putting on a make-ahead picnic sandwich?

I am cautious with excessive mayonnaise, salad dressing, very juicy tomatoes, undrained pickles, wet roasted vegetables, heavily dressed greens, and large amounts of fresh mozzarella that have not been drained. None of these ingredients is inherently bad; they simply require more attention when the sandwich will sit.

I also avoid building every picnic sandwich as high as possible. A giant sandwich may look impressive when freshly made, but if the filling falls onto the blanket with the first bite, it is not particularly useful. Compact, well-layered sandwiches usually travel and eat much better.

Final Thoughts

A good picnic sandwich does not need a long ingredient list or an unusual combination to deserve a place in the basket. I would much rather unwrap a well-made turkey and cheddar sandwich than discover that an overly ambitious sandwich has turned into wet bread and loose filling. The recipes I come back to—Italian pressed sandwiches, muffulettas, chicken salad, ham and Swiss, Caprese, pan bagnat, wraps, and simple deli sandwiches—work because they start with familiar flavors and pay attention to the practical details that matter outdoors.

If there is one picnic habit I would keep, it is building for the journey rather than only for the first five minutes after assembly. Drain wet ingredients. Use sturdy bread. Put cheese or lettuce between moisture and the bread. Go easy on dressing. Press sandwiches that benefit from pressing, and keep perishable fillings properly chilled. Those small choices do far more for a picnic lunch than chasing complicated recipes. When I can open the cooler several hours later and pull out sandwiches that are still neat, fresh, and genuinely inviting, I know I packed