If you have several hours to bake your beans, preheat the oven to 250°F. If you only have thirty minutes to an hour, set it to 350°F. Additionally, you can also cook the beans on the grill.
Drain all of the liquid from the can of baked beans into a measuring cup. Make note of the amount of liquid and discard. This is the amount of ketchup you will use.
Place the beans in the large bowl and add ketchup (an equal amount to the quantity of baked beans liquid you discarded, about 3/4 cup), mustard, molasses, salt, dry mustard, pepper, onion, and bacon, and stir to combine.
Transfer to a ceramic casserole dish (or disposable aluminum pan for cooking on the grill or bringing to a barbecue where you may not get your dish back), and bake for at least 1-2 hours at 250°F, or at least 30 minutes-1 hour at 350°F or on the grill, until heather through and thick and bubbly. The lower and longer you bake them, the better.