I make aluminum foil packs ahead of time and put them in the cooler. When I get there and get set up, I either throw them on a small grill or put them on the edge of the fire until they heat up.
I usually take a hamburger, put seasoning on it, throw in onions, carrot slices and potato slices and a dab of butter. Put it in two layers of aluminum foil and cook it about 30 minutes. Yummy.