We bring frozen leftovers and leave them in the SMB fridge to thaw while we are traveling. Keeps the fridge cooler as a side benefit. Prep is minimal.
We also like to take stuff that can be heated at least two ways (if it needs heating at all), because we never know if we will be boondocking or at a campsite with electric, or at a site that may/may not allow campfires. And if it involves dirtying more than one dish, it's off the list. We don't want a lot of effort for dinner when it comes to returning to the SMB after sunset after a long hike.
Every trip, we have a tradition of Kraft Mac'n'Cheese with ground beef mixed in, seasoned with Old Bay and cayenne. Re-heats in the micro or on the stovetop. Simple, clean, and satisfying.
Breakfast is cold cereal and milk, or hard boiled eggs. Lunches are usually ham or turkey sandwiches and chips. The only thing that needs refrigeration is the meat and cheese. Hummus packs easily, and can be eaten as a snack or used as a spread on a sandwich.
Quality canned, low sodium soup is good. Canned soup doesn't need to use valuable fridge space to store, and can heat on stove, nuked, or on a fire. Hot dogs and brats (quality ones) are a fave of ours, and are best cooked over a fire. You always have the lesser options of nuking or boiling them.
We've brought home made lasagna, ravioli, enchiladas, chollay (Afghan chick pea stew), all of which can be reheated multiple ways, but the micro is the best for these. Leftover pizza slices from our local favorite joint seemed like a good idea, but weren't...unless you like re-living your college days.
Don't forget to splurge on yourself once a trip. Our traditional splurge is a Denny's Moons Over My Hammy breakfast sandwich platter. Once you have that, you don't need to eat again until next Tuesday, nutritionally speaking.