Thermos Cooking Basics

Here are the basic steps for cooking food with a thermos:

Purchase a Quality Thermos

Your plastic Hello Kitty lunch thermos will not enough, I’m sorry to say. You need a quality metal thermos in order to retain enough heat to cook food. That doesn’t mean that a thermos will be expensive however. I use a quart size stainless steel Thermos brand thermos I bought at Walmart for around $25. It works great.

Pre-Heat Your Thermos

Before you start putting food into your thermos you need to preheat it with boiling water. This will heat up the metal in the thermos before you put your food in. This way, the water you put in with your food won’t be cooled down by having to heat up the thermos first (First Law of Thermodynamics, I think).

I like an electric kettle for quickly boiling water for this kind of work. It will boil water faster, safer, and easier than using your stove or the microwave.

Measure and Boil More Water

Most recipes will require boiling water to be added to the food for cooking. As soon as you start pre-heating the thermos, measure and start boiling the next amount of water that will be added to the food.

Prepare Food

While your water is set to boil start gathering the food you’re going to cook. Measure the grains or other ingredients and have them ready to dump into the thermos.

Combine and Wait

You don’t have to get crazy, but you want to empty the hot water out of the thermos, put your ingredients in, and then pour the boiling water in as quickly as you can. I use a canning funnel to help pour the ingredients into the thermos. You might even need a more narrow funnel if your thermos has a narrow opening.

Once you’ve poured all your ingredients into the thermos, close it up (don’t screw it down so tight it’s hard to open later), give it a nice shake to combine, and lay it down on its side on a counter.

Why not stand it up, you ask?

Well, you want the ingredients to stay in contact with the hot water as evenly as possible. If you stand the thermos up, the heavier food will sink to the bottom and will not cook as evenly.

For backpackers and campers:

When I’m out on the trail I try to insulate the thermos as best I can overnight. I either wrap it in some clothes or a jacket or I’ve even put it in my sleeping bag on colder nights.

When Is It Done?

It depends…

Oat groats take a lot longer to cook than steel cut oats. Wheat berries take longer to cook than cracked wheat.

The nice thing about thermos cooking is you can often tell if the food is done by the way it sounds when you give the thermos a shake. A few examples:

  • Quinoa – when you first put in the quinoa, salt, and water, it will slosh all around when you shake the thermos. In time it will thicken and then near the end it will barely move at all. When it barely moves it’s done!
  • Oats –  will slowly thicken during cooking and you can tell when they’re ready based on sound. They won’t ever thicken like the quinoa (not if you add the right amount of water!), but you’ll quickly learn when they’re done.

Don’t worry. You can always open up the thermos and take a look and we also give suggested cooking times. The nice thing about a thermos is that it’s very difficult to overcook anything and taking a quick peek once or twice isn’t going to release enough heat to cause a problem.


Once your food is done you can pour (or spoon) some onto your plate and then just leave the thermos with the rest of the food on the counter. It’ll sit there at the perfect temperature for hours! So you could prepare some oatmeal to enjoy early in the morning and then leave it on the counter for your kids or spouse to eat once they’re ready for breakfast.

It’s the perfect way to fix fast food that’s actually good for you.

17 thoughts on “Thermos Cooking Basics”

  1. Very much so, but consider more basic (read, healthy) ingredients like whole wheat pasta, barley soup, etc.

    I’ve got a lot of work to do in getting more recipes up on the site. Thanks for the feedback.

  2. This site could sure do with some more recipes. I’m trying to sell this concept of cooking to some adventure training students and with a shortage of recipes I don’t think it will go down too well.

  3. My son and another cadet in his squadron came up with a great thermos stew. They dehydrated some fresh veggies and grabbed some dried herbs and a few pieces of jerky and some similar flavor broth and boiling water.
    dumped it in their thermos’ and went off to a weekend event. The food served was not the best and everyone had watering mouths as these two chowed down on their stew. ( like i told the boys You may have to depend on your wits and creativity some day for a meal so get to figuring it out)

    John if a 13 yr old and 15 year old with little survival training; can come up with this then your adventure training students should start thinking outside the thermos and come up with their own recipes.

  4. I have used thermos cooking for years. Its great for travel — hotel room, etc. One other use besides grains is cooking eggs. You can have boiled in shell eggs by putting a couple of eggs in their shell into the thermos, adding actively boiling water and then setting that in a towel or other insulation for about 30 minutes. Best if the eggs are not directly from refrigeration. If they are, pour boiling water over them for a bit, pour it off and pour more boiling water over them to cover, then seal thermos and insulate.

  5. I like this concept, but after reading through these recipes I’ve concluded that it makes more sense for slower cooking items like steel cut oats. By the time I’ve boiled water twice on my stove top, I might as well have boiled the water and cooked my pasta in it on the stove. Would be more far appealing without that first step of preheating the thermos.

  6. I agree, Sara. The only exception might be where you want to fix yourself a lunch in the thermos where you dump everything in (pasta, canned chicken, some veggies, chicken stock) and let it cook while you’re working.

  7. Hallo Dave,

    Is it possible to cook beans in a thermos. They take a long time to cook so i’m really looking for a alternetive way……

  8. Helpful blog – thank you. How much of a bouillion cube would you put in a ~ 25 oz food thermos (.74 L) *or* 1.1L coffee thermos for homemade chicken soup? I know the answer would be subjective, depending on taste. Any experience with this?

  9. I keEP three large mouth thermoses. Always try to pre-warm your thermos, but add more cooking time if you can’t. A leaky Thermos must be always upright; but wrap it tightly in a towel to reduce heat loss. It will still work.

    I cook fuzzli pasta by putting my wide-mouth thermos half full of dry pasta, then mixing instant soup ( I like mushroom. but any flavour is good) according to directions; or, one packet for every 8 oz of water, and filling the thermos up to the brim with the soup. Cap, and If your thermos doesn’t leak ( old ones tend to) lay it on its side for 30 or so minutes. If your thermos leaks, open and stir from bottom quickly at 15 minutes and re-cap.

    use bullion cubes as per directions per 8 ounces of water. Know your thermos capacity, and you will know how much to use to make a thermos full or half-full to cook pasta in it.
    you can and should cook package ramen (not more expensive pot Noodles in a cup, which just makes more litter) in a thermos with the specified amount of water. allow 5 minutes, and see if it’s done. you may need more time. Then add seasonings as per directions.

    If my gas and electricity are cut off, I keep a stainless steel Kelly Kettle (expensive but worth it) to boil water and use it to boil water quickly to fill my thermos. A portable kelly kettle will burn anything, and is not dependent on propane, or liquid fuel, which in a crisis will be unavailable. Always burn Kelly Kettle outdoors, on a balcony or porch. If you must be a refugee, the Kelly Kettle and it’s little cook set are small, collapsible, and portable in its bag. Just remember to include Knife, fork, and spoon(s) in the bag so you don’t have to use twigs or fingers as cooking / eating implements. Also matches and a fire-steel which you Must to practice using beforehand so it will work for you when you run out of matches.

  10. Hello everybody, I have a system…
    I get out of bed, flick on my bedroom electric kettle, go into the washroom to get dressed. (I know that I will start racing to finish and wipe the sink up before the kettle boils.) Then I pour a bit of water into my tea travel mug and pour water into my food thermos to warm it up…. I use that same water to make the tea for my travel mug. I like that! It feels good to accomplish something personally interesting that quickly in a day or when I need to reboot my brain to work.
    I am off to prep some things to keep in a tin can in my room for lunches on the go or at my desk in my room.
    I tried a YouTube tip from a university professor who used to can alot. She dehydrates frozen small mixed vegetables or corn. They fit into jars nicely and can be added to soups and stews.
    Another tip…I made room in the fridge for a pot and I save water from cooking veggies or pasta. I sometimes use it again to make perogies.
    Before I sit down to eat, I add barley and leeks and/or chopped kale stems, and any dried veggies if I want. Also dry beans that I previously soaked, cooked, and froze or dehydrated and stored in jars after turning them over and over in oversized jars for three days for good drying. This pot goes into the fridge.
    Also, I found it easy to finely Slice carrots with a crank gadget and freeze for lentil soup with saved cooking water. I am going to try dehydrating those sluced carrots next….and butternut squash cubes, with corn, and parsnips……
    And apples doused in lemon…
    And slices of citrus for my water travel mug…

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