Preheat oven to 450 degrees F (230 degrees C). Sprinkle cornmeal onto a baking sheet.
Roll out dough to 1/4-inch thickness using a rolling pin on a work surface. Place dough on prepared baking sheet and brush olive oil thoroughly over surface. Layer dough with mozzarella cheese, butternut squash, and red onion. Sprinkle dough with Parmesan cheese and black pepper; top with garlic.
Bake in the preheated oven until golden brown, 25 to 30 minutes.