4 tbsp. vegetable oil
1 red onion, halved and thinly sliced
1 red bell pepper, thinly sliced
1 green bell pepper, thinly sliced
3 lb. sirloin, thinly sliced
1 tsp. all-purpose seasoning
1 tsp. garlic salt
8 hoagie rolls
5 tbsp. softened butter
7 1-ounce slices of provolone cheese
1. Preheat oven to 400 F. Add 2 tablespoons vegetable oil to a large, deep sauté pan and place over medium-low heat. Add onion and bell peppers. While the veggies are cooking, prepare the steak, stirring veggies occasionally.
2. Use a sharp knife to trim excess fat off of the sirloin and then slice it as thinly as possible across the grain. Chop the sliced steak into very small pieces.
3. When the veggies are tender, transfer them to a dish and return the skillet to the heat. Add additional oil and place over medium-high heat. Add half of the sliced steak and cook, stirring frequently, for about 4 to 5 minutes, or until no pink remains. Season with 1/2 teaspoon each seasoned salt and garlic salt while cooking. Transfer first batch of steak with a slotted spoon to dish with onions and peppers, leaving juice behind in pan. Add additional oil if needed and repeat with remaining steak and seasoning.
4. Split open the hoagies rolls but do not separate them. Spread them with the softened butter and place them on a baking sheet. Place the baking sheet in the oven and bake for 3 to 5 minutes or until lightly golden brown.
5. Drain out all of the liquid from the pan and return to the stove. Add back all of the steak and the onions and peppers. Place 7 provolone slices over the mixture in a circle and cover the pan. Cook on medium heat until cheese melts, then stir. Use tongs to transfer to the toasted sandwich rolls.