Preheat the oven to 350°F. Spray a 9×13-inch baking dish with nonstick cooking spray.
In a large bowl, combine all ingredients, reserving ½ cup of the shredded cheese for topping.
Spread the mixture evenly in the prepared baking dish.
Bake for 40–45 minutes, until the top is lightly browned.
Sprinkle the reserved ½ cup cheese over the casserole. Bake for 3–5 more minutes, until the cheese is melted.
Let cool at room temperature for 10–15 minutes. Top with fresh parsley before serving.
Notes
It is very important to thaw the hash browns before making this casserole. Refrigerate the leftover casserole in an airtight container for up to 5 days. This casserole can be prepped the night before. Refrigerate and let the casserole come to room temperature before baking.