Steel-cut oats and old-fashioned oats, the most popular types of oatmeal, look quite similar to oat bran. While both of these products come from the same grain, they have some key differences, including part of the oat grain that is used to make them, their nutritional values, and common methods of preparation.

Most oat products include the whole oat, but oat bran is only the outer layer of the oat grain that is essentially a byproduct of other oat products. Oat bran softens much faster than regular oatmeal, has a mushier texture, and tastes more nutty and flavorful; it also is more porous, meaning it cooks much faster than oatmeal.

Oatmeal and oat bran have a similar carb and fat content, but bran is significantly higher in fiber and protein, making it even more filling than oatmeal. While both oat bran and oatmeal help lower cholesterol and control blood sugar levels, oat bran is also lower in calories; however, this doesn't mean that bran is always the best choice.

When making overnight oats, oat bran expands much more than oatmeal and tends to get mushy, while oatmeal retains its bite, which is a preferable texture for some eaters. When preparing other dishes, oat bran should only be used in recipes where the final texture is intended to be soft and flaky, such as in granola.