Preheat oven to 350°F. Grease a 9×13 inch casserole dish with cooking spray.
Heat olive oil in large skillet over medium high heat. Add ground beef, onions and green peppers and cook, stirring often, about 7 to 9 minutes, until beef is no longer pink and veggies are softened.
Add tomatoes, mushrooms, black olives and oregano. Cook, uncovered, for 10 minutes, stirring occasionally.
Add half of the spaghetti to the bottom of the casserole dish. Top with 1/2 of the tomato/beef mixture. Sprinkle 1 cup of cheddar cheese on top. Repeat these layers a second time.
In a small bowl, mix together the cream of mushroom soup and water. Pour evenly on to the casserole. Top with Parmesan cheese.