01 - Preheat the oven to 375°F.
02 - Arrange bell pepper halves cut-side up in a baking dish and roast for 10 minutes to soften.
03 - Heat olive oil in a large skillet over medium-high heat. Add onions and mushrooms, sautéing until softened, about 5 minutes.
04 - Stir in minced garlic and cook for 1 minute until fragrant.
05 - Add sliced beef to the skillet. Season with salt, pepper, and Worcestershire sauce. Cook, stirring, until beef is just cooked through, 3 to 4 minutes.
06 - If using, stir in softened cream cheese until melted and evenly incorporated, then remove from heat.
07 - Remove roasted peppers from the oven and spoon the beef mixture evenly into each half.
08 - Place one slice of provolone cheese on top of each stuffed pepper half.
09 - Return to the oven and bake for 15 to 20 minutes until cheese is melted and peppers are tender.
10 - Serve the stuffed peppers hot.