Cut the bacon into half-inch pieces. In a large Dutch Oven or cast iron skillet over medium-high heat, brown the bacon to a medium crispness. Remove bacon from from skillet, transferring to a plate or bowl. Drain off the majority of the grease, leaving some grease in the skillet. Over medium-high heat, sauté the onion and pepper for 5-7 minutes or until onion is translucent.
To the onions and pepper, add in the baked beans, kidney beans, butter beans and bacon.
In a bowl, combine the tomato sauce, brown sugar, molasses, vinegar, Worcestershire, mustard, salt and pepper. Whisk together until combined. Pour over the bean mixture. Stir all ingredients together until well coated and combined.
Bring to simmer over medium-low heat. Reduce to low, and continue to simmer for 30 minutes, stirring occasionally. Serve right away.