Preheat oven to 350F degrees. Begin browning ground beef in a medium pan over medium heat.
Add in diced onion and garlic. Cook beef until brown and crumbled and onion is translucent. Drain excess fat from cooked ground beef.
In a large bowl, combine ground beef mixture, cans of baked beans, rinsed pinto and northern beans, crumbled bacon, ketchup, brown sugar, vinegar, salt and dry mustard.
Stir well. Then pour mixture into a 9x13 baking dish.
Cover with aluminum foil and bake at 350 degrees for about 45 minutes. Then remove foil and bake for additional 5-10 minutes.