3 large green bell peppers, halved lengthwise and seeded
1 (14 ounce) package thinly sliced frozen Philly beef steak
1 large sweet onion, diced
1 (6 ounce) package sliced baby bella mushrooms, diced
1 tablespoon olive oil
1 tablespoon minced garlic
1 teaspoon Montreal steak seasoning, or more to taste
6 slices provolone cheese
Preheat the oven to 400 degrees F (200 degrees C). Place bell peppers cut-side up on a baking sheet.
Heat a 12-inch skillet over medium heat. Cook and stir steak until lightly browned, about 10 minutes. Remove from skillet.
Add onion, mushrooms, olive oil, garlic, and steak seasoning to the skillet. Cook and stir until onions and mushrooms are nice and tender, about 5 minutes. Return the steak to the skillet and cook for 3 to 5 minutes more.
Spoon steak mixture into the bell pepper halves until full. Top with provolone cheese.
Bake in the preheated oven until cheese on top is golden brown, about 15 minutes. Let cool.