In a medium bowl, combine the tomato sauce, ketchup, Worcestershire sauce, mustard, and brown sugar, and set it aside.

Place a large skillet or Dutch oven over medium/high heat. Add olive oil and ground beef. Sauté the beef for about 5 minutes until cooked through and no longer pink, breaking it up with a spatula. If there is extra fat, tilt the pan and spoon it out or blot it up with paper towels. Season with salt and pepper.

Stir in the diced peppers and onion. Cook another 5 minutes until the veggies are tender and beef is browned. Add garlic and sauté 30 seconds until fragrant, stirring constantly.

Add the sauce and bring to a light boil. Reduce heat to low and simmer uncovered for about 10-15 minutes or until thickened to your liking. Adjust the seasoning and add water if you prefer a looser consistency. Serve on toasted buns.