Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes or until al dente; drain and reserve.
Preheat oven to 300 degrees F (150 degrees C).
In a large skillet, brown ground beef until no longer pink; drain reserving 1 tablespoon of drippings in pan. Set beef aside. In skillet saute onion, green bell pepper and garlic until just soft. Combine browned beef, ketchup, oregano, salt and pepper with onion mixture; mix well.
Pour mixture into a 9x13 inch baking dish. On top of mixture, layer pasta and then sprinkle on cheese. Bake in preheated oven until cheese is melted.
