Step 1

Preheat the Oven: Begin by setting the oven to a temperature of 350°F (177°C). It is crucial to allow the oven to reach the desired temperature before baking to ensure even cooking.

Step 2

Prepare the Baking Dish: Using a cooking spray, lightly coat an 11 x 14-inch baking dish to prevent sticking and ensure easy removal of the casserole once cooked.

Step 3

Combine Ingredients: In a large mixing bowl, combine the thawed hash browns with the melted margarine or butter. Add the finely chopped onion, sour cream, grated cheddar cheese, cream of chicken soup, salt, and pepper. Mix these components thoroughly to ensure that the hash browns are evenly coated with the creamy, cheesy mixture.

Step 4

Transfer to Baking Dish: Carefully transfer the mixture to the prepared baking dish. Spread the mixture evenly across the dish to promote uniform cooking.

Step 5

Bake the Casserole: Place the dish in the preheated oven and bake for approximately 45 minutes. The casserole should be golden brown on top and bubbly around the edges when it is fully cooked.