Brown hamburger and onion. Drain. Add garlic powder, oregano, salt and pepper. Cool mixture. Add Cheddar cheese, American cheese, and tomato soup. Let stand in refrigerator at least 4 hours. You may freeze mixture. To serve, place on 8 - 10 bun halves. Bake at 350° for 6 - 8 minutes or until cheese melts.
Servings: