Cook spaghetti according to package directions; drain. Add butter and Parmesan cheese; toss to coat. In a large bowl, combine the spaghetti sauce, green pepper and tomatoes.
In a blender, cover and process the ricotta cheese until pureed. Add to the spaghetti sauce mixture. Stir in the mushrooms, onion, garlic, basil, oregano and 1-1/2 cups mozzarella cheese. Add the spaghetti; toss to coat.
Transfer to a 13-in. x 9-in. baking dish coated with cooking spray. Sprinkle with remaining mozzarella. Cover; bake at 350° for 40-45 minutes or until heated through. Yield: 9 servings.