Preheat oven to 425 °F (205 °C) and line a large baking sheet with parchment paper. Microwave riced broccoli for 1 minute to steam. Carefully ring out extra moisture from the broccoli using paper towel or cheese cloth.
Transfer broccoli to a large bowl and add egg, 1 cup mozzarella, Parmesan, and garlic. Season with oregano, salt, and pepper. Transfer dough to baking sheet and shape into a thin, round crust.
Bake until golden and dried out, 20 minutes. Top with remaining 1/2 cup mozzarella and bake until cheese is melted and crust is crispy, 10 minutes more. Garnish with parsley and pepper flakes if using. Serve warm with marinara.
There are 411 calories in 1 serving of Broccoli Cheesy Bread.