- Preheat the oven to 350°F (175°C) and grease the 9x13 inch baking dish. 
- In a skillet over medium heat, cook the breakfast sausage until browned and fully cooked. Drain excess fat if necessary. 
- In a mixing bowl, whisk together the eggs, milk, salt, pepper, onion powder, and garlic powder until well combined. 
- In the greased baking dish, spread the frozen hash browns evenly across the bottom. 
- Layer the cooked sausage over the hash browns, followed by 1 cup of the shredded cheddar cheese. 
- Pour the egg mixture evenly over the entire casserole. 
- Sprinkle the remaining 1 cup of cheddar cheese on top. 
- Bake in the preheated oven for 45 minutes or until the cheese is melted and bubbly, and the eggs are set. 
- Allow the casserole to cool slightly before garnishing with chopped green onions if desired. Serve warm.