Brown the ground beef in a large skillet. Remove to a large bowl and discard the fat.
In the same skillet, cook the bacon. You can either chop it beforehand or crumble it afterward. Remove to a paper-towel lined plate. Discard all but 1 tablespoon of bacon grease from the pan.
Preheat the oven to 400 degrees F.
Saute the onions until they are translucent, about 5-8 minutes.
in a large bowl, combine ground beef, bacon, onions, baked beans, pork and beans, black beans, barbecue sauce, mustard, and Worcestershire sauce. Taste it. Add more BBQ sauce if you want.
Spread the beans into a 9x13 inch pan. Bake at 400 for 30 minutes.
Turn the oven down to 350 and cover the beans with foil. Bake for another 20-30 minutes.
I like mine extra crispy on top, so I broil them for a couple minutes, but that's not necessary unless you like slightly burned beans. (I mean who doesn't.) Serve hot!