Brown the ground beef over medium heat, breaking it up as it cooks.
When beef is partially cooked through, add the onion, pepper, and garlic to the pan and continue cooking and stirring until meat is fully cooked and vegetables have softened. Drain grease and return to the pan.
Add the ketchup, mustard, vinegar, brown sugar, Worcestershire sauce, salt, and pepper to a small bowl and whisk well to combine.
Pour the sauce over the ground beef and stir to coat.
Simmer the meat mixture for 5 minutes before spooning onto sandwich rolls.
Use any color bell pepper you prefer or leave it out entirely if you have picky eaters.