1Heat oven to 400°F. Spray 11x7-inch (2-quart) glass baking dish with cooking spray.
2In 12-inch skillet, cook beef and onion over medium heat 8 to 10 minutes, stirring occasionally, until beef is thoroughly cooked; drain. Stir in mixed vegetables, soup, pepper and 1/2 cup milk. Heat to boiling. Pour into baking dish.
3In medium bowl, stir Bisquick mix and dry mashed potatoes. In small microwavable bowl, microwave 2 cups milk on High 2 minutes. Stir hot milk into Bisquick mixture with fork until soft dough forms; let stand 2 minutes. Drop dough by 15 spoonfuls onto hot beef mixture.
4Bake 25 to 30 minutes or until dumplings are cooked and lightly browned.