Preheat your oven to 375°F (190°C). Gather your ingredients and equipment.

In a large skillet over medium heat, cook chopped onions and pork sausage until browned, about 5-7 minutes.

Drain excess fat and set aside the sausage-onion mixture.

In a mixing bowl, combine thawed hash browns, sausage-onion mixture, and shredded cheddar.

In another bowl, whisk together eggs, milk, salt, pepper, and garlic powder. Pour into hash brown mixture and fold to combine.

Transfer mixture to the greased baking dish, smoothing out the top.

Bake for 45-55 minutes until edges are golden brown and center is set.

Let cool for 5 minutes, slice, and garnish with green onions before serving.