Casseroles generally don't need to be refrigerated, but it depends on the ingredients. For instance, if your casserole contains mayonnaise or other dairy products, it should be refrigerated.
Kitchenwares that contain cooked meat or poultry can also be refrigerated. If you're not sure whether your stainless steel kitchenware utensils needs to be refrigerated, check the manufacturer's instructions.
Casseroles are a great way to cook food in an oven. They're simple to use and can be made from a variety of materials. Be sure to check the manufacturer's instructions before storing your casserole.