Oatmeal is a type of coarse flour made of hulled oat grains (groats) that have either been milled (ground) or steel-cut, or else it refers to rolled oats. Ground oats are also called "white oats". Steel-cut oats are known as "coarse oatmeal", "Irish oatmeal" or "pinhead oats". Rolled oats can be either thick or thin, and may be categorized as "old-fashioned", "quick", or "instant", depending on the cooking time, which is shortened by the size of the oats, precooking, and sometimes the addition of enzymes.
The term oatmeal is also used in the U.S. and parts of Canada to describe a popular oat porridge made from either ground, steel-cut, or rolled oats.
Rolled oats are steamed and flattened whole oat groats. Old-fashioned oats can be thick and take a while to boil to make porridge. Quick-cooking rolled oats (quick oats) are cut into small pieces before being steamed and rolled. Instant oatmeal is cooked and dried, often with a sweetener, such as sugar, and flavourings added.
Both types of rolled oats may be eaten uncooked, as in muesli, or may be cooked with water or milk to make porridge. In some countries, rolled oats are eaten raw or toasted with milk and sugar, sometimes with raisins added, like a basic muesli. The term "oatmeal" sometimes refers to a porridge made from the bran or fibrous husk as well as the oat kernel or groat. Rolled oats are often used as a key ingredient in granola breakfast cereals (in which toasted oats are blended with sugar and/or nuts and raisins) and granola bars.
Rolled oats are also used as an ingredient in oatmeal cookies, oatcakes, British flapjack bars, and baked oatmeal dessert dishes such as Apple Brown Betty and apple crisp. Oats may also be added to foods as an accent, as in the topping on many oat bran breads and as the coating on Caboc cheese. Oatmeal is also used as a thickening agent in thick, savoury Arabic or Egyptian meat-and-vegetable soups, and sometimes as a way of adding relatively low-cost fibre and nutritional content to meatloaf.
Unenriched oatmeal, cooked by boiling or microwave, is 84% water, and contains 12% carbohydrates, including 2% dietary fiber, and 2% each of protein and fat (table). In a 100 gram amount, cooked oatmeal provides 71 Calories and contains 29% of the Daily Value (DV) for manganese and moderate content of phosphorus and zinc (11% DV each), with no other micronutrients in significant content (see table on right).
Oatmeal and other oat products were the subject of a 1997 ruling by the Food and Drug Administration that consuming oat bran or whole rolled oats can lower the risk of heart disease when combined with a low-fat diet via the effect of oat beta-glucan to reduce levels of blood cholesterol. A similar conclusion was reached in 2010 by the European Food Safety Authority.
Staffordshire oatcakes are a local component of the full English breakfast. It is a plate-sized pancake, made with equal parts medium oatmeal and wheatmeal (flour), along with frothing yeast. Once the mixture has risen to produce something like a Yorkshire pudding batter, it is ladled onto a griddle or bakestone, and dried through. Staffordshire oatcakes are commonly paired with bacon, sausages, mushrooms, kidney, and baked beans, among others. A related oatcake is sometimes found in neighbouring Derbyshire.