How to Make It
Preheat oven to 375°F. Quarter pizza dough; cover. Dust a baking sheet with flour. Warm 1 Tbsp. oil in a skillet over medium heat. Add onion and bell pepper, season with salt and pepper and sauté until tender, about 5 minutes. Remove to a bowl. Warm 1 Tbsp. oil in skillet. Sauté mushrooms until they give up their liquid, about 4 minutes. Add to bowl; stir.
Roll each piece of dough into an 8-inch circle. Spread 1/4 cup sauce onto each round, leaving a 1/2-inch border. Divide vegetables and olives among rounds; sprinkle with mozzarella.
Fold rounds in half, pressing to seal. Sprinkle calzones with pepper and Parmesan. Transfer to baking sheet and bake 15 to 20 minutes, until golden brown. Serve.