Linda in MO posted 05-01-99 
Source:  Taste of Home 
  Baked Spaghetti 
  1 c. chopped onion 
  1 c. chopped green pepper 
  1 (28 oz.) can tomatoes, with liquid, cut up or crushed
  1-2 (4 oz. each) cans mushrooms, stem and pieces, drained 
  1 small can black olives, drained (optional) 
  2 t. dried oregano 
  1 lb. ground beef, browned and drained (optional) 
  12 oz. spaghetti, cooked and drained 
  2 c. (8 oz.) shredded cheese or cheddar/mozzarella blend 
  1 can condensed cream of mushroom soup 
  1/4 c. water 
  1/4 c. grated Parmesan cheese 
In large skillet sprayed with non-stick cooking spray, saute onions and green pepper until tender. 
Add tomatoes, mushrooms, olives, oregano, and ground beef. Simmer, uncovered for 10 minutes. 
Place half of the cooked spaghetti in a 9x13 baking dish that has been sprayed with non-stick cooking spray. Top with half the vegetable and meat mixture. 
Sprinkle with half of the cheddar. Repeat layers. Mix soup and water in a bowl. 
Pour over casserole and sprinkle with Parmesan cheese. Bake uncoverd at 350 fo 30-35 minutes or until heated through.