It is super easy to freeze a casserole, either before or after it’s cooked. If baked, allow the casserole to cool fully before wrapping it up in a layer of plastic and freezing for up to 3 months. When ready to eat or cook, simply thaw the casserole overnight in the fridge and bake as directed or reheat until warm throughout. Use aluminum containers if you plan on freezing the casserole as they’re lighter, and you won’t risk thermal shock on ceramic dishes.