Whether you're cooking tuna casserole as a make-ahead freezer meal, or end up with leftovers, preparing the casserole properly for long-term freezing is key. Several variations of the tuna-rice bake or tuna-noodle casserole exist, allowing you to sock away more than one kind of starchy tuna meal.
If you're making the casserole ahead of time, skip the oven-baking stage of your favorite tuna casserole until you're ready to serve. Once you've combined the cooked starch and tuna with a creamy binder and vegetables, put the saucepan or mixing bowl into a basin of ice water to cool it quickly. It will then be ready to be spooned into a freezer bag. When you're ready to serve the tuna casserole, defrost the mixture in the refrigerator overnight, put a crunchy topping on it and bake at the recommended time and temperature.
Leftover Tuna Technique
Leftover, oven-baked tuna casserole can also be frozen. The trick is to flash-freeze the leftovers for a few hours in the original baking dish, or a smaller one, then prepare it for long-term freezer storage. Don't allow leftover tuna casserole to sit at room temperature for more than two hours. Cover the untouched portion of the casserole with aluminum foil, and freeze it in the baking pan for several hours. Once it is solid, remove the casserole from the pan, place it in a freezer bag, and return it to the freezer. Cook the thawed casserole at the same time and temperature called for in the original recipe. Check the internal temperature on any tuna casserole reaches 165 degrees Fahrenheit before you serve it.