Cooking Whole Oat Groats

Whole oats groats are oats in their least processed form. All that is been done is the husk has been removed. Groats have a nice chewiness and great nutty flavor.

Our instructions will make more sense after you quickly read through our thermos cooking basics.

Basic Recipe

Ratio: 1 part oat groats to 3 parts water
To taste – try 1/2 teaspoon per cup of oats to start (put the salt in after the oatmeal is cooked)
Cooking Time: overnight


  1. Boil enough water to fill up your thermos. I like to use an electric kettle, but use the stove or whatever else you have.
  2. While it’s heating, get your ingredients ready.
  3. Once your water boils, fill up your thermos, close the lid, and set aside.
  4. Measure out your water, keeping a 1:3 ratio. But make sure to leave room in the thermos for the oats to expand. For my 5 cup thermos I was using 1.5 cups oats and 3 cups water and it was too much. Leave at least a cup of expansion room.
  5. Boil your measured water.
  6. When your water is about ready to boil, pour the water out of the thermos.
  7. Put the oats in the thermos and pour the boiling water over them, close it up, give in a few shakes, and lay it down on the counter.

Because the oats are in whole form they need to cook overnight. But what could be more convenient than getting breakfast ready the night before!


  • Don’t add the salt until the oatmeal is cooked. This produces a creamier oatmeal because an element within the oat – pentosan – can combine with the water and make a creamier texture. Using salt during cooking will keep the water from interacting with the pentosan. Just sprinkle the salt on the oats in your bowl or into the thermos.
  • Make a lot! There’s no reason to make a cup or two of oatmeal. Make as much as your thermos can hold and leave the rest in the thermos for someone else to discover or put it in a container in the fridge and eat it tomorrow. It heats up great in the microwave.

Learn about the nutritional value of oats.


Watch this excellent show from Alton Brown’s “Good Eats” about why you hold the salt until the oats are cooked. Alton Brown is my personal hero.

12 thoughts on “Cooking Whole Oat Groats”

  1. This recipe calls for a 2:1 ratio of water to oats, but the steel cut recipe calles for a 3.5:1 ratio. What ratio would you recommend to begin Thermos cooking?

    Thanks for the website!


  2. Justin – That’s a great question. Initially I cooked whole oats with a 2:1 ratio, but really a 3:1 ratio works better.

  3. Justin – That’s a great question. Initially I cooked whole oats with a 2:1 ratio, but really a 3:1 ratio works better.

  4. We sell organic whole grain of all kinds and learning more about oats all the time. We are currently making oat milk smoothies from oat groats ground in our flour mill. We then sift the bran out and save for other uses. The remaining oat flour makes a great oat milk. We like it because we have never been a fan of soy milk, and it is a nice substitute.

  5. This is an awesome concept! Darrold, how do you sift out the bran, and what do you use it in? I think making the oat milk would be a fun experiment for the kids!

  6. Good website! I truly love how it is simple on my eyes and the data are well written. I’m wondering how I could be notified whenever a new post has been made. I have subscribed to your RSS feed which must do the trick! Have a great day!

  7. I normally make porridge at the 3:1 ratio using 1.5 parts milk, same water, and 1 part oats. The idea of making porridge on water alone, hmmm, nerrrrr.

    Have you ever tried making proper porridge, rather just gruel (water and oats). The latter is, in the UK at least, likened to Dickensian prison food. Urrrh!

  8. So do these recipes work well in the narrower, 61 oz. Nissan thermos, and are they more difficult to clean? We currently have a narrow mouth Stanley.

Leave a Comment