It also depends on how long you're staying. Some things keep better than others.
Very easy:
Tinned meals (stew, chili, pork & beans) heated over the fire.
Hot dogs or pre-cooked sausages heated on sticks over the fire or on the grill.
Pasta and a jar of sauce is easy if you have a stove, not so easy on a grill or fire ring.
Very easy sides: tinned veg (pierce the tin and you can heat it directly in the coals), bag of salad from the grocery store, raw cut up veggies and dip, fruit, rolls.
Almost as easy:
Steak, chops, hamburgers, chicken pieces are easy to cook on the grill or on a grate over the fire, but bringing them requires a bit more care since they are raw and can spoil. We usually season/marinade in advance, shape the burgers, and freeze. They do double duty as ice in the cooler.
Sliced zucchini, bell peppers, tinned pineapple rings, peaches cut in half can all be grilled easily with delicious results. If you can make a foil tray or packet you can cook smaller things on the grill: shrimp, mushrooms, broccoli.
Sometimes the cooking is part of the fun. At least once every trip we have a big camping breakfast: build a fire, cook bacon, cook eggs and pancakes in the bacon grease. It takes most of the morning.
You do want a way to heat water efficiently. Mornings and evenings can be chilly compared to when you live indoors, so hot drinks will be welcome.