Heat the oven to 350°F.
Cook the bacon in a large oven-safe skillet or Dutch oven over medium heat for 5–6 minutes, until it starts to crisp. Add the onion and cook for 3–4 minutes, until soft. Spoon off all but about 1 tablespoon of the drippings.
Stir in the beans, ketchup, brown sugar, mustard, Worcestershire, vinegar and pepper.
Bake uncovered for 45–50 minutes, until thick and bubbly around the edges. If your pan isn’t oven-safe, pour the beans into a 2-quart baking dish first.
Let stand for 10 minutes before serving.