Preheat oven to 425°F; line a baking sheet with parchment paper, or coat with a non-stick cooking spray.
Divide dough into four equal parts; press or roll each ball to ~⅛-inch thick circle.
Spoon and spread sauce on each circle; leaving½ -inch around the edges clear.
Distribute onions, mushrooms and sausage on one half of each circle; top with shredded mozzarella cheese.
Fold the dough over the toppings and crimp the edges; transfer to prepared baking sheet.
Brush each with olive oil; cut air vents in each calzone; sprinkle with Parmesan cheese, if desired.
Bake ~15 minutes, until calzone is golden brown.
