Start by preheating your oven to 400°F.

Cut the bell peppers in half lengthwise, removing seeds and ribs.

Lightly spray a 9x13-inch casserole dish with non-stick spray, then place the peppers in the dish.

Bake the peppers, open side up, uncovered for 15 minutes.

Meanwhile, warm a large skillet over medium-high heat.

Melt the butter in the skillet, then add the sliced onions and mushrooms.

Sauté for about 5 minutes, stirring occasionally, until the mushrooms release their juices.

Add in the minced garlic and cook for another 30 seconds, just until fragrant.

Transfer the onion-mushroom mixture to a bowl and set aside.

Season the steak slices with salt and add them to the hot skillet.

Sprinkle with your preferred steak seasoning, and cook the meat for around 3 minutes, stirring occasionally.

Return the onion-mushroom mixture to the pan and stir to combine.

Once the peppers are done, remove them from the oven.

Place a slice of provolone cheese into each pepper half, pressing it down to fit the shape.

Generously fill each pepper with the steak mixture, then top with another slice of cheese.

Broil the stuffed peppers for about 3 minutes, keeping an eye on them, until the cheese is melted and bubbly.

Finish by garnishing with the chopped parsley.

Serve immediately and enjoy! 🍴