In a large skillet, cook beef and onion over medium heat until meat is no longer pink; drain. Stir in the soup, Italian seasoning, salt and pepper.
Transfer to a greased 9-in. square baking dish. Sprinkle with the vegetables. In a bowl, combine mashed potatoes and cheese; spread over vegetables. Bake, uncovered, at 350° for 30 minutes or until bubbly. Yield: 4 servings.