Preheat the oven to 350° and spray an 11x7 baking dish with non-stick cooking spray. Set aside.
In a large cast iron pan, over medium heat, add Italian sausage (with casing removed). Crumble sausage as it cooks and add in diced onions. Cook until sausage is no longer pink and onions are tender. Add 1 cup of shredded cheese and stir until cheese is melted. Remove from heat and set aside.
Cut biscuits into quarters and flatten/roll out each quarter. (You should end up with 40 pieces of flattened biscuit dough.)
Fill each piece of biscuit dough with a spoonful of sausage mixture. Pinch edges of the biscuits together to seal and roll each into a ball. Repeat until all biscuits are filled with mixture.
Place each filled biscuit into the prepared baking dish.
In a separate bowl, add eggs, milk, pepper, and garlic powder. Whisk well until eggs are completely beaten.
Pour egg mixture over biscuits
Place in preheated oven and bake for 50-60 minutes or until eggs are completely cooked through.
Remove from oven and top with remaining shredded cheese. Serve immediately.