Mix ground beef, onion, bell pepper, and garlic together in a large bowl; add bread crumbs, egg, cayenne pepper, salt, and black pepper and mix.
Stir mustard and Worcestershire sauce together in a small bowl; add to meat mixture and mix. Shape the meat mixture into an 8x4-inch loaf and place on a rimmed baking sheet. Spread olive oil over the top and sides of the loaf.
Bake in the preheated oven until no longer pink in the center, about 1 hour. An instant-read thermometer inserted into the center should read at least 160 degrees F (70 degrees C). Transfer meatloaf to a platter and cut into 8 slices.
