Preheat your oven to 350°F (175°C).
In a large frying pan over medium heat, cook the breakfast sausage until browned and crumbled, about 5-7 minutes. Drain any excess fat and set aside.
In a large mixing bowl, whisk together the eggs, milk, salt, black pepper, garlic powder, and onion powder until well combined.
Grease the 9x13 inch baking dish. Spread the thawed hash browns evenly in the bottom of the dish.
Sprinkle the cooked sausage over the hash browns evenly.
Pour the egg mixture over the sausage and hash browns, making sure to cover everything evenly.
Top with shredded cheddar cheese and chopped green onions (if using).
Bake in the preheated oven for 35-45 minutes, or until the eggs are set and the top is lightly golden.
Allow to cool for a few minutes before slicing and serving.
For customization, consider adding vegetables such as bell peppers or spinach for added nutrition and flavor.
This dish can be assembled the night before and stored in the refrigerator; simply bake it in the morning for a convenient breakfast option.