In bowl, combine cauliflower, egg, mozzarella, Parmesan, garlic powder and oregano, season with salt and pepper. Using your fingers, transfer cauliflower mixture to piece of parchment paper and press into 12-inch circle. Slide parchment paper with cauliflower crust onto hot baking sheet from preheated oven. Bake until crust is golden brown, 13 to 15 minutes.