In a skillet, cook ground beef, onions, garlic and green pepper over medium heat until meat is no longer pink; drain. Add the beans, barbecue sauce, brown sugar, ketchup and mustard. Simmer for 5 minutes or until heated through.
Transfer to a greased 11-in. x 7-in. x 2-in. baking dish. Separate biscuits and cut in half; arrange over beef mixture. Bake, uncovered, at 400° for 18 minutes or until biscuits are golden. Sprinkle with cheese; bake 2-3 minutes longer or until cheese is melted.