In a large skillet, brown the ground beef over medium heat until fully cooked.
Drain excess fat from the skillet.
Add chopped onion and bell pepper to the beef, cooking until soft.
Stir in minced garlic and cook for 1 minute.
Mix in ketchup, Worcestershire sauce, brown sugar, and mustard.
Season with salt and pepper, adjusting to taste.
Reduce heat and let the mixture simmer for about 10 minutes.
Toast the hamburger buns lightly.
Spoon the beef mixture onto the bottom half of each bun.
Top with the other half of the bun and serve immediately.