Preheat the oven to 350°F (175°C).

In a large skillet over medium heat, cook the breakfast sausage until browned and fully cooked. Drain excess grease.

In a large mixing bowl, whisk together the eggs, milk, salt, pepper, garlic powder, and onion powder until well combined.

Add the thawed hash browns, cooked sausage, bell peppers, and half of the shredded cheese to the egg mixture. Stir until everything is evenly coated.

Pour the mixture into a greased 9x13 inch baking dish and spread it out evenly.

Top with the remaining shredded cheese and chopped green onions.

Bake in the preheated oven for 45-50 minutes, or until the casserole is set and the top is golden brown.

Let it cool for a few minutes before slicing and serving.