Saute onion & green pepper in margarine in. Add tomatoes, oregano, garlic and beef. Simmer for 10 minutes. Stir occasionally to keep from sticking.
Place 1/2 cook spaghetti in bottom of 9 X 13 inch greased pan. Top with 1/2 of veg/meat mixture. Next top with 1 cup mozzarella cheese and repeat layers. Mix soup and water together and spread over casserole. Top with Parmesan cheese.
Bake uncovered on 350 degrees for 30 minutes.
Easy to make ahead and freeze for busy days!