Heat oven to 375°F. Generously spray bottom and sides of 15x10x1-inch pan with cooking spray. In 12-inch skillet, cook beef and onions over medium heat, stirring occasionally, until beef is thoroughly cooked; drain. Stir in soup, vegetables and milk.
2.
In large bowl, stir Bisquick mix and water until moistened. Spread evenly in pan. Spread beef mixture over batter. Sprinkle with cheese.