Step 1Heat the oven to 450 degrees. Lightly dust 2 baking sheets with cornmeal and set aside.
Step 2Divide the pizza dough into 4 even portions. Roll each into a ball and then flatten into a disk shape. Lightly sprinkle a work surface with a little cornmeal and, using a floured rolling pin, roll each disk into a 9-inch circle about 1/4-inch to 1/8-inch thick.
Step 3Divide the marinara sauce among the circles of dough, spreading it around the center of the dough and within 1 inch of the edges. Divide the meatballs among the circles, placing them on the lower half of each piece of dough.
Step 4Cover the meatballs evenly with the grated cheese. Fold the top half of the dough over the filling and press the edges together, crimping with your fingertips. Set 2 calzones on each baking sheet. Brush the tops with the olive oil.
Step 5Bake the calzones until nicely browned, about 12 to 15 minutes. Serve hot or warm.