Step 1: Prepare the Vegetables. Heat 1 tablespoon of olive oil in a large skillet or cast-iron pan over medium-high heat. Add the thinly sliced onions and bell peppers. Sauté for 8-10 minutes, stirring occasionally, until softened and lightly caramelized. Remove the vegetables from the pan and set aside.
Step 2: Cook the Steak. If necessary, add another teaspoon of oil to the same skillet. Increase heat to high. Add the thinly sliced steak in a single layer (cook in batches if needed to avoid overcrowding). Season with salt, black pepper, garlic powder, and dried oregano. Cook for 2-3 minutes, stirring frequently, until the steak is browned and cooked through. Avoid overcooking to keep it tender.
Step 3: Combine Filling. Return the cooked vegetables to the skillet with the steak. Stir to combine thoroughly. Reduce heat to low to keep the mixture warm.
Step 4: Assemble the Quesadillas. Lightly brush one side of a flour tortilla with melted butter. Place the tortilla, butter-side down, in a clean, dry skillet over medium heat. Sprinkle half of one side of the tortilla with a generous layer of shredded provolone cheese.
Step 5: Add Filling and More Cheese. Spoon a portion of the steak and vegetable mixture over the cheesy half of the tortilla. Top the filling with more shredded provolone cheese.
Step 6: Cook the Quesadilla. Fold the plain half of the tortilla over the filling, pressing down gently with a spatula. Cook for 3-4 minutes per side, or until the tortilla is golden brown and crispy, and the cheese is completely melted and gooey. You may need to press down on the quesadilla to ensure even browning and melting.
Step 7: Repeat and Serve. Remove the cooked quesadilla from the pan and let it rest on a cutting board for a minute before slicing into wedges. Repeat with the remaining tortillas and filling. Serve immediately and enjoy your delicious philly cheesesteak quesadilla recipe!