Preheat oven to 350 and grease a 9x13 baking dish. Cook the ground beef, onion, and garlic in a skillet over medium heat, until the beef is browned and the onions are tender. Drain any excess fat.
Combine the cooked ground beef mixture, baked beans, ketchup, brown sugar, Worcestershire sauce, mustard, salt, and pepper in a large mixing bowl. Mix well to combine.