Preheat oven to 400°F. Grease a 9x13 baking pan. In a large bowl, whisk together flour, garlic powder and oregano. Add the milk and eggs and gently stir until thoroughly combined. Add the pepperoni and cheeses and stir in with a wooden spoon or rubber spatula until evenly distributed.

Pour mixture into prepared baking dish and spread into an even layer. Bake until golden brown and bubbling, 30-40 minutes. Let sit for at least 15 minutes before cutting and serving.