Freezing a prepared casserole dish can be a time-saving and convenient method for a quick dinner, and is especially useful for weeknight meals or to feed surprise house guests. Regardless of your particular recipe for hash brown casserole, you can freeze the dish either before you bake it or after it has come out of the oven and cooled. A properly frozen hash brown casserole will keep for up to three months.
Prepare the hash brown casserole according to your favorite recipe. Depending on the amount of time that you have and your preference, you can either bake the casserole and then freeze it, or simply freeze it uncooked. If you do decide to bake it first, do not bake it for the full time. If the recipe requires 40 minutes of baking time, pull the casserole out of the oven after 30 minutes and allow it to cool completely. This will prevent the casserole from overcooking when you reheat it.
Wrap the casserole dish with freezer wrap or heavy-duty aluminum foil. Both wraps are effective for withstanding freezing temperatures, in addition to preventing freezer burn.
Write the date on a piece of masking tape and attach the tape to the top or side of the casserole dish. A frozen hash brown casserole should keep for up to three months.
Allow the casserole dish to thaw completely before baking or reheating. When the casserole has finished thawing, you can smell it and observe whether it has spoiled or separated. If it looks and smells okay, and it has not been in the freezer for over three months, bake the casserole according to your recipe, or reheat it in an oven at 350 degrees Fahrenheit until golden brown.