Preheat your oven to 400 degrees Fahrenheit. It’s important to have a hot oven ready for optimal baking.
Heat a large pan over medium-high heat. Add 1 tablespoon of vegetable oil to the pan, letting it warm up just enough to create a sizzle.
Once the oil is hot, add the steak to the pan. Sprinkle with salt and pepper to season. Cook for about 2 to 3 minutes, just until the steak begins to brown.
Next, add the sliced onions, bell pepper, and mushrooms to the pan. Sauté these for another 2 to 3 minutes until the onions are lightly browned. You want the veggies tender but still crisp.
Remove the pan from heat. With everything cooked, transfer the mixture to a bowl and let it cool slightly. This will prevent the mozzarella cheese from melting prematurely.
On a clean surface, take one loaf of pre-made pizza dough and roll it out into a rectangle approximately 9 by 13 inches. Use a rolling pin for an even thickness.
Pour the cooled steak mixture into the center of the rolled dough, leaving about a half-inch border around the edges. This space is crucial for sealing the Stromboli.
Layer the mozzarella cheese on top of the steak mixture, making sure to cover it generously. If using provolone cheese, add that on top as well for an extra cheesy bite.
Now, fold in the sides of the dough and tuck and roll it from the bottom up to form your Stromboli. Make sure it’s sealed well to prevent any filling from spilling out.
Place the rolled Stromboli seam side down on a greased baking sheet or lined with aluminum foil. This will help it bake evenly and come off easily.
Beat the egg and brush it over the outside of the dough to give it a beautiful golden color as it bakes. Cut thin 2-inch strips on the top layer of the dough for a decorative touch.
Bake the Stromboli in your preheated oven for 15 to 20 minutes or until it turns golden brown and the dough looks crispy.
Once baked, remove from the oven and let it cool for a few minutes. Cut into slices and serve immediately with your favorite dipping sauce, like ranch or marinara.