Preheat the oven to 350°F (175°C). Grease an 11×17-inch baking dish.
Carve small faces into the peppers. Remove and reserve the tops, then remove the cores, seeds, and membranes.
Lightly mix the beef, egg, bread, onion, tomato, garlic, chili sauce, mustard, Worcestershire sauce, salt, and pepper.
Divide the mixture among the peppers. Add the reserved tops and arrange the peppers upright in the prepared dish.
Bake for approximately 55–70 minutes, targeting about 1 hour, until the peppers are tender and the filling reaches 160°F (71°C).
Rest for 5 minutes before serving.