1 lb. lean ground beef, 1 sweet onion (chopped), 1/2 cup ketchup, 3/4 cup brown sugar, 1 T. vinegar, 1 t. dry mustard powder, 1 (16 oz.) can baked beans, 1 (15.5 oz.) can kidney beans, 1 (15 oz.) can butter beans, 1/2 lb. bacon.
Cook bacon & drain, break into medium pieces, set aside. Brown beef & onion, drain off fat. Preheat oven 350 degrees.
In a large bowl mix bacon & beef mixture with all other ingredients. Do not drain liquid from canned beans. Mix well.
Place mixture in 13" x 9" baking dish and bake for 1 hour uncovered.