Spray 13x9-inch (3-quart) glass baking dish or 3-quart oval casserole with cooking spray. Spread 1/3 of the bread cubes in baking dish. Top evenly with 1/3 of the bell pepper and onion stir-fry and 1/3 of the beef. Sprinkle with 1/3 of the cheese. Repeat layers twice, ending with cheese.