Preheat the oven to 325 degrees.
In an oven safe skillet or dutch oven, add the olive oil, peppers and onions. Cook for 3-4 minutes until the onions are translucent.
Add the ground beef. Cook, break up the meat, until no longer pink.
Add the beans, Worcestershire sauce, brown sugar, ketchup, and mustard. Stir until the ingredients are thoroughly combined.
If you don't have an oven safe skillet, transfer the bean mixture to a 9x13-inch baking pan.
Transfer to the oven and bake for 45 minutes. Stir the beans halfway through.