Preheat oven to 220 degrees C. Let dough rise then punch down and divide into 4 pieces.
On a floured surface, roll each piece of dough into a long oval shape. Spread each with sauce, then layer with ham, salami and pepperoni. Sprinkle with garlic powder then top with mozzarella, onion, mushrooms and capsicum. Bring the long sides together over the centre and pinch together to seal. Turn over, so that the seam is on the bottom, and place on an ungreased baking tray. With a sharp knife, cut 3 diagonal slices to allow the steam to escape.
Bake in preheated oven for 20 to 30 minutes, or until golden brown.