Baked Spaghetti Casserole

Why I Love This Recipe
This not-so-typical baked spaghetti casserole recipe was given to me by a lady I work with; it originally comes from Taste Of Home, and was submitted by Ruth Koberna of Brecksville, OH.
*Instead of cooking the ground beef and vegetables separately, I cooked them together until the meat was brown and the veggies were tender.
Ingredients You'll Need
1 cup onion, chopped
1 cup green pepper, chopped
1 Tbsp. butter or margarine (I used non-stick cooking spray)
2 (14 oz.) cans diced tomatoes, undrained
1 (4 oz.) can mushroom stems and pieces, drained
1 (2 1/4 oz.) can sliced ripe olives, drained
2 tsp. dried oregano
1 lb. ground beef, browned and drained*
12 oz. spaghetti, cooked and drained according to package directions
2 cups (8 oz.) Cheddar cheese, shredded
1 (10 3/4 oz.) can condensed cream of mushroom soup
1/4 cup water
1/4 cup grated Parmesan cheese
Directions
Preheat oven to 350 F.
In a large skillet, saute onion and green pepper in butter or margarine until tender; add tomatoes, mushrooms, olives and oregano.
Add ground beef and simmer, uncovered, for 10 minutes.
Place half of the spaghetti in a greased 13 X 9-inch baking dish (again, I used non-stick cooking spray); top with half of the vegetable mixture.
Sprinkle with 1 cup of Cheddar cheese; repeat layers; whisk the soup and water until smooth and pour over casserole.
Sprinkle with Parmesan cheese; bake uncovered in preheated oven for 30 to 35 minutes, or until heated through.