Preheat your oven to 350°F (175°C) and lightly grease a 9x13-inch baking dish.

In a large skillet, heat over medium heat and cook the breakfast sausage for about 5-7 minutes until browned.

Drain any excess fat and spread the cooked sausage evenly across the bottom of the baking dish.

Layer the thawed hash brown potatoes evenly on top of the sausage.

Sprinkle half of the shredded cheddar cheese and half of the sliced green onions over the hash brown layer.

Whisk together the eggs, milk, salt, black pepper, and garlic powder until smooth, then pour over the layers in the baking dish.

Sprinkle the remaining cheddar cheese and green onions on top of the egg mixture.

Bake in the preheated oven for 35 to 40 minutes until the eggs are set and the top is golden brown.

Let the casserole rest for 5 minutes before slicing to help it hold its shape.

Slice into squares and serve warm, perfect for breakfast or brunch.