Prepare the Cheddar Bay Biscuit Dough

1. Preheat the Oven: Preheat your oven to 375°F (190°C) and grease a 9×13-inch baking dish.
2. Mix Dry Ingredients: In a medium bowl, whisk together the flour, baking powder, salt, and garlic powder.
3. Cut in the Butter: Add the cold, cubed butter and use a pastry cutter or fork to combine until the mixture resembles coarse crumbs.
4. Add Cheese and Buttermilk: Fold in the shredded cheddar and buttermilk until a soft dough forms.
5. Press into Dish: Press the dough evenly into the prepared baking dish as a biscuit base.

Prepare the Egg Mixture

1. Whisk Eggs and Seasonings: In a large bowl, whisk together eggs, milk, salt, pepper, and onion powder.
2. Add Cheese, Bacon, and Green Onions: Stir in shredded cheddar, crumbled turkey bacon, and chopped green onions, if using.

Assemble and Bake

1. Pour Egg Mixture: Pour the egg mixture evenly over the biscuit base in the baking dish.
2. Bake: Bake in the preheated oven for 30-35 minutes, or until the eggs are set and the top is golden.
3. Cool Slightly and Serve: Let the casserole cool for a few minutes before slicing and serving.