Preheat your oven to 350°F (175°C). This will ensure it’s hot and ready for your casserole.
Prepare a baking dish by greasing a 9x13 inch glass baking dish with cooking spray or butter.
In a large bowl, combine the 30 ounces of frozen hashbrowns, 1 cup of sour cream, 1 can of cream of chicken soup, and 1/2 cup of melted butter. Mix well until all ingredients are thoroughly combined.
Add the flavor ingredients: Stir in the 2 cups of shredded cheddar cheese, 1/2 cup of diced onion, 1/2 teaspoon garlic powder, 1/2 teaspoon black pepper, and 1/2 teaspoon salt. Ensure that the cheese and seasonings are evenly distributed through the mixture.
Spoon the mixture into your prepared baking dish, spreading it evenly. Use a spatula to smooth the top.
Bake in the preheated oven for about 45 minutes, or until the top is golden brown and the casserole is heated through. You should see bubbly edges indicating it’s just right!
Allow to cool for 10 minutes before serving, as this will help the casserole set up a bit.