Steel-cut oats, also known as pinhead or Irish oats, differ from the more common rolled oats in the way the grain is prepared. For steel-cut oat, the individual grains, also known as groats, are chopped with a blade; for rolled oats, the grains are flattened into flakes. Steel-cut oats take longer to cook than rolled oats, but many people think they possess superior flavor and texture.
Storing Uncooked Oats
Because steel-cut oats are a whole-grain product, they need to be stored carefully or the oil in the grain can go rancid. Rancid oats smell like old cooking oil. In some environments, steel-cut oats must also be protected from insect infestation and from being eaten by rodents. The ideal way to store steel-cut oats for the long term is to pour them into a glass or plastic container, seal tightly and freeze them. They keep in the freezer for up to 4 months. You can also store your container of uncooked oats in the refrigerator for up to 3 months; keep the container tightly sealed to protect from excess moisture. Uncooked steel-cut oats may also be stored in a cool, dry place for about 2 months, according to the Whole Grains Council.
Storing Cooked Oats
Because steel-cut oats take up to 30 minutes to prepare, it can be convenient to cook ahead of time and store the cooked oats in the refrigerator until you're ready to reheat and serve them. Cook a large batch of oats, divide them into individual portions, package them in a covered bowl or plastic bag, and store them in the refrigerator for up to 5 days.
Freezing Cooked Oats
Cooked oatmeal can also be successfully frozen for storage. Frozen oatmeal will keep for up to 3 months. Freeze it in individual portions to make later serving easier; you won't have to defrost the whole batch just to have a single bowl of oatmeal.
Reheating Cooked Oatmeal
Whether it's coming from the refrigerator or freezer, oatmeal reheats easily. In fact, experts at The Kitchn think steel-cut oatmeal improves in texture and flavor after spending time in the refrigerator. Add a splash of liquid such as milk, cream or water to help loosen it up while reheating on the stove or in the microwave. Stir it in thoroughly to incorporate, cover, heat until thoroughly warmed, then serve as you would freshly cooked oatmeal.