Preheat the Oven: Preheat your oven to 375°F (190°C) and grease a 9x13-inch baking dish with non-stick spray or butter.
Cook the Bacon: In a skillet, cook bacon until crispy. Let it cool, then crumble it into small pieces.
Prepare the Hashbrowns: Thaw the hashbrowns and pat them dry with a paper towel to remove excess moisture.
Layer the Casserole: Spread the hashbrowns evenly in the greased baking dish. Sprinkle the crumbled bacon and shredded cheddar cheese over the hashbrowns.
Mix the Egg Mixture: In a large mixing bowl, whisk together eggs, milk, garlic powder, salt, and pepper. Pour this mixture evenly over the hashbrown layer.
Bake: Cover the casserole dish with foil and bake for 25-30 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the eggs are fully set and the top is golden brown.
Garnish and Serve: Let the casserole cool for 5 minutes. Garnish with chopped green onions and serve warm.