Preheat oven to 450 degrees F. Coat a 3-quart casserole dish with cooking spray.
In a large skillet over medium heat, cook ground beef, onion, and bell pepper 8 to 10 minutes, or until no longer pink. Drain off excess fat. Add tomato sauce, Worcestershire sauce, vinegar, brown sugar, mustard, garlic powder, salt, and pepper. Cook 5 to 6 minutes, or until heated through. Pour into casserole dish and set aside.
In a small bowl, stir together baking mix and milk. Dollop 5 equal spoonfuls of batter onto meat mixture.
Bake 13 to 15 minutes, or until biscuits are golden brown and firm in center.