Preheat oven to 325F. Place the bell pepper halves in a casserole dish and cover with foil. Bake in the oven for 20 minutes. Remove and set aside
While the peppers are cooking, heat a large skillet over medium. Add the oil, onions, and mushrooms. Season with salt and pepper. Let sauté until soft.
Push the sautéed onions and mushrooms to one side of the pan and add the steak. Season with salt and pepper. Cook the steak until browned on both sides. About 5 minutes. Remove from heat.
To assemble: place a slice of cheese into each bell pepper half. Add the steak mixture, then another slice of cheese.
Set your oven broiler to HI and broil the stuffed peppers for 3-5 minutes or until the cheese starts to brown and bubble. Watch carefully so the don't burn! Serve immediately.
Notes
for 1 serving: 475 Calories / 32g fat / 10.4 carbs / 3.7g fiber / 37.8g protein