Preheat your oven to 400°F. Arrange the halved peppers in a baking dish, cut-side up. Lightly drizzle with oil and roast for 18–20 minutes while you prepare the filling. This step softens the peppers and keeps them from being too firm after baking.
In a large skillet over medium-high heat, melt the butter or heat the olive oil. Add the sliced onions and diced green peppers. Cook for 5–7 minutes until softened and lightly golden. Stir in the minced garlic and cook for another minute.
Push the vegetables to one side of the skillet. Add the ground beef and break it apart with a wooden spoon. Cook until browned and fully cooked through. Drain excess grease if needed.
Combine the beef and vegetables. Add Worcestershire sauce, cracked black pepper, garlic & onion powder, smoked paprika and a pinch of salt. Let everything cook together for 2–3 minutes so the flavors come together.
Remove the pre-roasted peppers from the oven.Place half a slice of provolone at the bottom of each pepperFill each pepper generously with the beef mixture, pressing lightlyTop with 1 to 1½ slices of provolone cheeseReturn to the oven and bake for 15–20 minutes, until the cheese is melted, bubbly, and golden on top. Let the stuffed peppers rest for about 5 minutes before serving. Garnish with fresh parsley, dried oregano or a sprinkle of extra black pepper if desired.