01 - Preheat oven to 400°F. Arrange bell pepper halves cut side up in a baking dish.
02 - Heat 1 tablespoon olive oil in a large skillet over medium heat. Add onions and mushrooms; sauté 5-6 minutes until softened. Add garlic and cook 1 minute more.
03 - Push vegetables to the side of the skillet. Add remaining olive oil and sliced beef. Sauté 3-4 minutes, stirring, until just cooked through. Stir in Worcestershire sauce, salt, and pepper. Mix beef and vegetables together, then remove from heat.
04 - Place one slice of provolone cheese into the bottom of each pepper half.
05 - Evenly fill each pepper with the beef and vegetable mixture. Top with another slice of provolone.
06 - Cover the baking dish with foil and bake for 20 minutes.
07 - Remove foil and bake for an additional 10-15 minutes, until peppers are tender and cheese is melted and slightly golden. Serve hot.