Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13 inch baking dish.
In a large skillet over medium heat, cook the ground beef until brown. Add the onion and garlic; cook until the onion is tender. Drain off excess fat.
In a large bowl, combine the pork and beans, kidney beans, black beans, ketchup, brown sugar, Worcestershire sauce and mustard. Add the ground beef mixture.
Pour into the prepared baking dish. Top with crumbled bacon.
Bake in preheated oven for 1 hour or until bubbly.