In a large skillet over medium heat, sauté the diced onion and green bell pepper in a drizzle of olive oil for about 5 minutes until softened.

Add the ground beef to the skillet and cook until browned, breaking it apart as it cooks for about 8 minutes. Drain excess grease if necessary.

Stir in ketchup, brown sugar, mustard, Worcestershire sauce, salt, and pepper; mix well to combine all ingredients.

Reduce heat and let the mixture simmer for 10 minutes to meld flavors together.

Toast hamburger buns under the broiler until golden brown.

Spoon the Sloppy Joe mixture onto each bun and serve warm.