Cooking Steel Cut Oats

Steel cut oats (also called pinhead oats, Scotch oats, or Irish oats) are such a step up taste and texture that there’s no comparison to rolled or instant oats. That’s because steel cut oats are made from whole oat groats that have been cut into smaller pieces. In comparison, instant oats are steamed and rolled so they cook more quickly. Instant oats also have a taste and consistency similar to glue. Ick.

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

Basic Recipe

Ratio: 1 part steel cut oats to 3.5 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: 40 minutes (approx.)


  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 1:3.5 ratio. You can use between 3 and 4 cups water for each cup of oats, but I think 3 1/2 cups is perfect.
  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.

Timing (40 minutes) is approximate. It partly depends on what kind of oatmeal consistency you’re after. Just give the thermos a shake every once in a while. It will slosh around at first, then it will slowly thicken.

You can always open the top and check inside once or twice until you get a feel for it. Remember that you can’t overcook oatmeal in a thermos, so don’t worry about watching the thermos or emptying it when it’s done. Just leave it on the counter and eat it when you’re ready. You can even put it out the night before – convenient, isn’t it?


  • 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.
  • Toast the oats before cooking. While you’re waiting for the water to boil you can toast the oats in a pan with a bit of butter or oil (I use a bit of olive oil). Toasting produces a nice flavor (subtly sweeter and caramelized). Try it out.
  • 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.
  • Make it the night before. What would be better than waking up and having a nice thermos full of hot oatmeal waiting for you. Just prepare it the night before and leave it on the counter. It’ll be hot and delicious whenever you’re ready for it.

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.

15 thoughts on “Cooking Steel Cut Oats”

  1. Why is it necessary to fill the thermos with water first, and then pour that water out? Why not just keep it empty until it’s time to add the hot ingredients?

  2. Yeah I was wondering the same as above, I read it over and over trying to figure out why you’d want to waste a whole Thermos of hot water?? Some clarification would be great because I will definitely be going out and buying a Thermos to start cooking my oats!

  3. Oh I get it, you’re assuming that the inside of your thermos is made of metal. This might be the case but most thermos’ are made out of glass on the inside which I doubt will need heating up in the same way. I’ll get back to you on that one when I find out. 🙂

  4. You need to bring the thermos up to temperature before starting the cooking process or else too much heat will be lost. That would mean a longer cooking time. The oatmeal needs to be brought up to temperature which will reduce the temperature in the thermos. You don’t want to lose more heat to the thermos itself, even if glass.

  5. Thermos cooking is all about heat retention. You pour out the water because it has lost some energy when it heated up the cold thermos. This is most critical on longer cooking recipes – like using whole oat groats that cook overnight vs. something that cooks more quickly.

    Experiment to see what will work best for you on what you’re making.

  6. Here in the U.S. you’ll be hard-pressed to find a thermos made out of glass any longer. Almost all of them are made from metal (though they still have a vacuum, of course). Not sure what is common in the U.K.

  7. it’s important to heat the thermos up really hot. if you don’t get the contents inside hot enough, and you leave it to cook over night. bacteria could grow in it and give you food poisoning. any time you put some hot food into a thermos for a long period of time., the thermos should be heated with boiling water and whatever hot food you put in it has to be boiled as well. once you get it in the thermos shake it around a little, this kills any bacteria. they follow the same process any time any food is canned or put in jars. then if you leave your thermos over night. it’s safe to leave in the container, until you open it. once opened you have to eat all of it. or refrigerate any leftovers

  8. This is the first time I have ever heard of thermos cooking, and I am entirely intrigued. I am going to be trying this with whatever cereals I have around. I always keep an assortment of various rolled grains (which I love, whether oats or spelt or barley or rye or wheat or kamut or whatever) and other cracked grains like Scottish oats and bulgar. Mix as desired. Time to go make breakfast…

  9. So are you saying I shouldn’t use my plastic thermos? I’m going to try it tonight, but would like to hear back in the event that I need to invest in a new thermos.

    If that is the case, could you recommend a good one? I’m making enough oats for one person, basically a way of making breakfast before I go to bed to ensure that I eat breakfast…

  10. I did this last night in an expensive Stanley thermos. Heated it ahead of time with boiling water. Poured out the hot water, put in my oats, put in new boiling water. Put the lid on tight. This was about 10 pm.

    Woke up this morning around 6:30 am and yes, the oats were done, but were lukewarm. Disappointed 🙁 My goal is not to have to dirty another pot. Suggestions?

  11. I’ve made thermos oatmeal for myself and my boyfriend almost every night for several years. It’s easy and reliable. He likes his soupy – 1.5 cups of water to 1/3 cup of steel cup oatmeal. I like mine more solid – 1.5 cups of water to 1/2 cup of oatmeal plus 1/4 cup dried fruit, plus salt, chia, etc. It’s possible to get a much thicker, drier consistency than could be made on a stove, almost like cooked rice instead of porridge.

    This technique isn’t limited to oatmeal. It works for cooking every type of grain I’ve tried. Preheating is a necessity. Don’t open the lid until it’s time to eat. The oatmeal is usually still warm for six or seven hours, but I think it’s fine tepid. If I don’t eat it that morning I take off the lid so it can cool down, cover it with plastic film, and put it in the fridge, then empty it in a bowl and microwave it.

  12. I have been using this recipe when I travel. Unfortunately, I think that the comment than you cannot overcook oats is wrong. Cooking many foods raises the glycemic index, I discovered. I suspect this is true of oats, although I have not found any direct evidence. In future trips I think I will cook groats overnight instead of steel cut oats.

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