Dice potatoes and fill casserole 3/4 full. Put layer of chopped onion over. Sprinkle a layer of chopped green pepper. Sprinkle 3 tablespoons uncooked rice on top. Put a layer of shredded American cheese over all. Mix up your favorite meatballs and fry slightly, then place on top of cheese. Heat 1 can cream of mushroom soup and 1/2 can Carnation milk and pour over the meatballs, using a fork prick through the ingredients. Add more milk if necessary, then bake about 1 hour at 350 degrees.