The Key To Microwaving Leftover Tuna Casserole Without Drying It Out

Tuna casserole is a hallmark of traditional American cooking, originating in the 1930s in Washington from a recipe submitted to a magazine (via Taste). It was in the 1940s that Campbell Soup made it a staple recipe associated with their company, and the 1950s that the dish became common in households across the country, according to Quaint Cooking.

The original recipe involves combining canned cream of mushroom soup, milk, peas, canned tuna, egg noodles, and bread crumbs together in baked casserole style, per Family Cookbook Project. People have added their own variations of different soups, cheeses, and vegetables, and other ingredients since its mid-century debut, though.

The dish gained and maintained its popularity and iconography in American households due to how affordable and easy to make it is, requiring little effort other than mixing together packaged or canned ingredients, which results in a meal with enough sustenance to feed your whole family. 

But if you find yourself with leftover tuna casserole, reheating it in the microwave can easily dry it out. Luckily, there's a quick and easy tip to keep your reheated tuna casserole as moist as it was fresh out of the oven.

While reheating your tuna casserole in the oven may result in a more evenly heated dish, it can be very inconvenient. The microwave is quicker, but runs the risk of cold spots and a dried out casserole. But this latter problem can be addressed and easily fixed.

According to Cook Clean Repeat, all you need is a cup of water. Portion out your leftover tuna casserole on a microwave safe plate or bowl, and add a small microwave safe cup or bowl filled with water alongside it. Microwave for a minute, stir or flip, and microwave for another one to two minutes. Repeat until the casserole is cooked all the way through. The water will evaporate into steam, keep the casserole moist, and help cook it through more evenly. They also recommend cutting the casserole serving into smaller pieces for more even cooking, as well as letting it sit out for 30 minutes before reheating. 

Alternatively, Foods Guy recommends adding a splash of water or chicken stock to your casserole and covering it with plastic wrap before microwaving, which will add new moisture and lock in the steam, ensuring a perfectly moist reheated tuna casserole.