Step 1: Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Step 2: In a large skillet, heat olive oil over medium heat. Add the sliced onions and bell peppers (if using) and sauté until softened, about 5 minutes. Add the thinly sliced beef to the skillet, season with salt and pepper, and cook until browned, about 5-7 minutes. Remove from heat and let cool slightly.
Step 3: Stir in the shredded provolone cheese and softened cream cheese into the cooled beef and vegetable mixture until well combined.
Step 4: On a lightly floured surface, unroll the refrigerated pizza dough and stretch it into a rectangle about 1/4-inch thick. Cut the dough into long strips, approximately 2-3 inches wide.
Step 5: Place a generous spoonful of the beef and cheese mixture onto one end of each dough strip. Fold the dough over the filling and press the edges firmly to seal. Place the stuffed breadsticks seam-side down on the prepared baking sheet.
Step 6: Sprinkle shredded mozzarella and grated Parmesan cheese over the top of the breadsticks. In a small bowl, mix the melted butter, garlic powder, and Italian seasoning. Brush this mixture evenly over the cheese-topped breadsticks for added flavor and a golden finish.
Step 7: Place the baking sheet in the preheated oven and bake for 15-20 minutes, or until the breadsticks are golden brown and the cheese is bubbly and melted.
Step 8: Once baked, remove the breadsticks from the oven and let them cool for a few minutes. Sprinkle chopped fresh parsley over the top for a fresh garnish. Serve warm with marinara sauce for dipping.