A quick lesson in types of oats (see comments).
Definition: According to a definition in Samuel Johnson's 1755 Dictionary of the English Language, oats were "a grain which in England is generally given to horses, but which in Scotland supports the people." Since oats are by far the most nutritious of the cereal grasses, it would appear that the Scots were ahead of the rest of us. Today, whole oats are still used as animal fodder. Humans don't usually consume them until after the oats have been cleaned, toasted, hulled and cleaned again, after which time they become oat groats (which still contain most of the original nutrients). Oat groats can be cooked and served as cereal, or prepared in the same manner as rice and used as a side dish or in a dish such as a salad or stuffing. When steamed and flattened with huge rollers, oat groats become regular rolled oats (also called old-fashioned oats). They take about 15 minutes to cook. Quick-cooking rolled oats are groats that have been cut into several pieces before being steamed and rolled into thinner flakes. Though they cook in about 5 minutes, many think the flavor and texture are never quite as satisfying as with regular rolled oats. Old-fashioned oats and quick-cooking oats can usually be interchanged in recipes. Instant oats, however, are not interchangeable because they're made with cut groats that have been precooked and dried before being rolled. This precooking process so softens the oat pieces that, after being combined with a liquid, the mixture can turn baked goods such as muffins or cookies into gooey lumps. Most instant oatmeal is packaged with salt, sugar and other flavorings. Scotch oats or steel-cut oats or Irish oatmeal are all names for groats that have been cut into 2 to 3 pieces and not rolled. They take considerably longer to cook than rolled oats and have a decidedly chewy texture. Oat flour is made from groats that have been ground into powder. It contains no gluten, however, so--for baked goods that need to rise, like yeast breads--must be combined with a flour that does. Oat bran is the outer casing of the oat and is particularly high in soluble fiber, thought to be a leading contender in the fight against high cholesterol. Oat bran, groats, flour and Scotch oats are more likely to be found in health-food stores than supermarkets. Oats are high in vitamin B-1 and contain a good amount of vitamins B-2 and E.
--Copyright (c) 1995 by Barron's Educational Series, from The New Food Lover's Companion, Second Edition, by Sharon Tyler Herbst