Potatoes
Onions
Garlic
Olive oil (if you're real poor, any oil will do)
Any other vegetable in season or available

Cut onions and potatoes, garlic and any other vegetables into slices about 1/4 inch thick. Stir to coat with oil. Put all these onto a big, thick sheet of aluminum foil and close up tight, sealing all of it into the foil. Cook on hot coals if possible, or in a hot oven until done, about 40 minutes.