Old-fashioned rolled oats are made by steaming oat groats and rolling them into flakes. By steaming and rolling the groats, the healthy oils are stabilized, which allows the oats to cook faster and stay fresh longer.
When raw oats are harvested, they can be processed in many different ways to produce whole oat groats, steel cut oats, Scottish oatmeal, instant rolled oats and oat flour.
Whole oat groats are also known as grain kernels, and these are the least-processed of the options. These oats are removed from the inedible hulls and cleaned, and they can be purchased from health food stores.
Steel cut oats are also known as Irish oatmeal, and they are made by cutting whole oat groats into two or three pieces with a steel blade. They are typically quicker to cook than the whole oat groats because the water is better able to penetrate the oats.
Scottish oatmeal is produced by stone grinding whole oat groats, making them quicker to cook than the whole oats.
Instant rolled oats are steamed and flattened like rolled oats, but they are rolled thinner or steamed longer than the regular variety.
Oat flour is made from finely ground oats, and it is used for baking and thickening purposes.