Preheat your oven to 400°F (200°C). Prepare a baking sheet by lightly greasing it with cooking spray.
In a skillet over medium heat, cook the ground beef until browned, breaking it apart as it cooks. Drain excess fat if necessary.
Add the chopped onions, bell peppers, and mushrooms to the skillet with the ground beef. Cook for about 5-7 minutes, or until the vegetables are tender.
Stir in the garlic powder, salt, and black pepper. Remove the skillet from heat and let the mixture cool slightly.
Roll out the pizza dough on a floured surface into a rectangle, about ¼ inch thick.
Spread the beef and vegetable mixture evenly over half of the dough. Sprinkle the provolone and mozzarella cheeses on top of the beef mixture.
Fold the other half of the dough over the filling, pressing to seal the edges. Trim any excess dough if desired.
Cut the stuffed dough into strips, about 1-2 inches wide, using a knife or pizza cutter.
Transfer the strips to the prepared baking sheet. Brush the tops with the beaten egg to give them a golden color when baking.
Bake in the preheated oven for 15-20 minutes or until the breadsticks are golden brown and cooked through.
Allow the breadsticks to cool for a few minutes before serving.