01 - Preheat the oven to 375°F and prepare a baking dish by lining it with parchment paper or greasing lightly.
02 - Place bell pepper halves cut side up in the prepared baking dish.
03 - Heat olive oil in a large skillet over medium-high heat and cook onions for 2 to 3 minutes until softened.
04 - Stir in mushrooms and diced green bell pepper, sautéing for an additional 3 to 4 minutes until tender.
05 - Add minced garlic and cook for 30 seconds until fragrant.
06 - Add the sliced beef, Worcestershire sauce, salt, and black pepper. Sauté for 3 to 5 minutes, stirring frequently, until beef is browned and cooked through. Remove from heat.
07 - Place one slice of provolone cheese inside each pepper half.
08 - Evenly divide the beef mixture among the pepper halves, pressing gently to fill.
09 - Add another slice of provolone cheese on top of each stuffed pepper.
10 - Cover the dish with aluminum foil and bake for 25 minutes. Remove the foil and bake an additional 5 to 7 minutes until the cheese is bubbly and golden.
11 - Allow to cool slightly before serving.