How Oats Are Processed

Oat grains and bowl of rolled oats

Oats are a staple of the American diet found in oatmeal, bread, cereal, granola, and many other foods, but there is complex process behind getting the oats from the soil to the table. There are a variety of steps to transform oats to oatmeal.

Oat Milling Step-by-Step

Usually, eating foods in their raw form is thought to be healthier, but oats must be processed from their raw form to even be edible. The initial step to processing oats is milling, which cleans, purifies, and preserves the oats. The milling of oats comprises of three smaller processes that all oats go through known as cleaning, hulling, and kilning.


Cleaning eliminates all unwanted materials from the oats. Oats pass under magnetic separators and through a rotating screen which removes scraps, sticks, stones, corn, etc. Finally, oats go through aspiration and a dry stoner extracting hulls, lighter, low grade oats, pebbles, and other grains.


After cleaning, oats must be dehulled, as the hulls of oats are indigestible. To remove the hull, rotating discs fling oats into rings that cause the hull to fall off without damaging the rest of the oat. This remaining oat is known as a groat.

Once cleaned and hulled, groats go through another round of aspiration, using air to blow off the remaining hulls. A paddy separator then separates the groats from any unhulled oats that may have snuck through.


In the process of kilning, steam and extended heat are applied to the groats. Kilning provides the toasted, browned flavor to the oats, extends the shelf life, and prevents the growth of harmful bacteria. Whole groats are the final product of kilning. They look similar to the grain farro.

How Oats Become Edible

Once oats go through milling, they are processed into household staples, such as steel cut oats, rolled oats, and instant oats.

Steel Cut Oats

Whole groats are simply chopped into two to four pieces to create steel cut oats. The groats go through a rotating, bladed machine that slices the groats, resulting in steel cut oats.

Rolled Oats (Old Fashioned Oats)

To produce rolled oats, whole groats are first steamed to soften the grain, then rolled through roller flats to flatten them, and finally pushed though a stream of air to dry the oats. Rolled oats can vary in thickness, which allows for the different variations seen in stores.

Instant Oats

The most processed of the oat are instant oats. These oats go though more steaming and rolling to produce much thinner and flatter oats. These oats are also pre-cooked via steam, thus the name "instant oats" and cook the fastest of all oat varieties.

Oat Processing

The milling and processing of oats are critical components to make the oats seen in stores today. Without cleaning, hulling, kilning, rolling, and steaming, oats could be indigestible, rotten, and contaminated with many unwanted materials. Steel cut, rolled, and instant oats are all products of oat processing and get their varying characteristics from that process.

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How Oats Are Processed