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Whenever I cook oatmeal (whether steel cut oats in a rice cooker or pan, or rolled oats in the microwave), it always overflows. How do you prevent this?

Do you just use a bigger container? Do you just take the pan off the heat or bowl off the microwave when it's about to overflow? I've also heard that if you put dried fruit or something like that along with the oatmeal while cooking, that helps prevent it from overflowing -- is this true?

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  • Right now, the question has 15 visible answers with more-or-less different suggestions, and 13 deleted ones which are mostly one-liners duplicating something that's already been said. If you want to post an answer, please read through the existing answers and only post if you have a new, different suggestion. If this request sounds absurd (too much work!) then please don't post anything, rather than making it even worse for everybody else by adding yet another post.
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    Oct 13, 2022 at 11:18

15 Answers 15

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A bigger container is definitely the 'instant' solution.

I've never hear of fruit preventing overflow. I'd guess the theory there is that it has something to do with the fruit interfering with the bubble to prevent them from forming...but I'd doubt it without A LOT of fruit.

Generally I've done two methods:

  • Reduce the power and increase the cooking time. Cut the power by 30% or so and increase the cooking time, this seems to prevent as much of a rapid boil and alleviates the problem.

  • Determine the time right before it starts to boil over, cut power off, cover it tightly and just let coast the rest of the way. This is particularly effective if you're cooking in a vessel with good thermal retention.

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  • I have a cheap digital thermometer that I put into liquids. When it reaches 95ºC it'll beep. I have no idea at what temp the oat will overflow. Oct 22, 2011 at 21:50
  • @BaffledCook good call!
    – rfusca
    Oct 22, 2011 at 21:51
  • After not making oatmeal in the microwave for a considerable time — and after upgrading to a new higher-wattage microwave — I tried making some the way I always had previously: half power, cook twice-as-long, stir halfway; but the results were disastrous. Tried again in a steep-walled covered container…same mess. Although I was skeptical, after seeing the same advice over at Cook's Illustrated, simply switching from a 6- to a 9-inch diameter bowl worked perfectly (using the half-power technique).
    – martineau
    Dec 31, 2021 at 15:25
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Simply add a handful of raisins and it will not boil over. Have no idea why but it works.

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  • 2
    And here I had been putting the raisins in afterwards... not only did this work for me, but I was able to cook at 100% power in half the time and didn't have to buy a larger bowl!
    – Michael
    Oct 2, 2019 at 16:38
  • Most likely, the raisins break the surface tension created by the water+starch.
    – Joe M
    Nov 19, 2020 at 19:14
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    but then you have raisins in your oatmeal
    – njzk2
    Jan 4, 2022 at 21:53
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Adequate room for expansion is important. For oatmeal I don't bother to do anything special, just know how long I can set the microwave for without getting a volcano in the bowl, and set it there, or watch it carefully (and shut it off) if going longer - it's only a couple of minutes. Portion size needs to be consistent so that time is consistent, or you need to know what time is "safe" for each portion size.

What I don't see in the current answers to this rather old question:

Steel cut oats were a trial for me via traditional direct heat methods - wanting stirring, prone to boilover, takes a long time that I don't want to spend stirring and pot-watching. They do expand a lot, so you need to measure quantity and allow for that in bowl size, and provide adequate water. But no stirring, no boilovers, no fuss and no problem if left on longer than needed (so long as the pot does not boil dry) when I steam them (in a bowl over boiling water in a lidded pot) rather than trying to direct-heat cook them in a pot or microwaving a bowl. Just get the pot simmering and come back in 15-20 minutes to cooked oats.

If you tend to cook oatmeal (rolled oats) a lot longer than I do, the steaming method might be worthwhile for that as well. I only bother with it for steel cut, since I don't cook rolled oats very long anyway.

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Bowl size is important. With milk or starchy products go for a wider bowl to stop overflowing

Generally ceramic or glass bowls work better than plastic, as they seem to absorb heat from the rising bubbles as slow them down

Add sugar after cooking, sugar will make for more sticky bubbles that will keep rising

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I never have an issue with oatmeal boiling over when I put cinnamon in the oatmeal before cooking it (in the microwave). I use extra thick rolled oats. I set the microwave at 60% power for 4:30 minutes, but even so, if I forget the cinnamon it will boil over.

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Since you didn't mention how you cook your oatmeal, I'll use the ways I've cooked mine as a reference for how to answer your question.

I usually cook old fashioned oats (lacking those I use quick oats) with brown sugar in milk, on the stovetop (but I used to do it in the microwave). I've done it in water before, but not enough to where I want to say much about it. I add a fair amount of milk, but I cook it until most of it's absorbed on the stovetop (I made it soupier when I cooked in the microwave).

In my observations, oatmeal will overflow if you cook it on high heat for too long.

For the stovetop, if you use a lower heat and cook it longer, or turn it down before too long, you shouldn't have particular problems (and you'll be less likely to burn your milk that way on the stovetop). On our stovetop, on one of the two larger burners (in a glass or stainless steel pot), it doesn't overflow if the heat is set on 4 (with the options being, from lowest to highest, these: low, 1, 2, 3, 4, 5, 6, 7, 8, 9, high; 5 is medium heat).

For microwave cooking, there's a sweet spot you just have to learn to find, and I don't remember what point that was. Stop cooking it before it overflows, and expect it to overflow if you cook it too long. (I didn't deal with temperature settings or anything; so, there are other microwave solutions, I'm sure).

FYI, I'm not recommending using a microwave for oatmeal (although it can taste pretty great). I personally think it's healthier to cook oats and other grains longer than the microwave allows palatably.

I have found that some substances can change the consistency of things like milk porridge. I'm not sure that fruit prevents boiling over, but it's possible. I know food grade diatomaceous earth seems to reduce curdling (like if you boil some jam in your oatmeal, the jam might cause it to curdle into acid cheese), anyway.

Edit: An even better option than the stovetop can be to bake your oatmeal. It just rises a bit, but it doesn't flow over or anything. The milk doesn't burn this way, either, and you don't have to stick around while it cooks. I'm not sure the ideal length of time to bake, but I cook it in a small glass or ceramic casserole-type pan on 450° F. in a toaster oven on the bake setting for less time than I expected. Keep a watch on it the first few times to get an idea of how long to cook it.

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What liquid are you cooking your oatmeal in? I ask this because when i first started eating oatmeal i was using milk and the microwave and i was having the same exact problem. Recently, i started just cooking the oatmeal in water and haven't had that problem since. I use a flavored oatmeal (i recommend the Maple and Brown Sugar weight control from Hy-Vee!!!) and it tastes just as good to me whether i cook it with milk or water.

rfusca is right about the larger container being an instant solution. I also have a theory about the type of container you use. I'll spare the details but at first, i was using a plastic bowl, overflow like clockwork, i switched to a porcelain bowl since, no overflow. It seems to cook better in the porcelain also. Haven't tried glass yet.

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I see four factors at work here:

  1. Vessel size: Choose a pot or bowl with plenty of room for foam to expand without overflowing.
  2. Heat control: If you can keep the heat just below a full boil, it's much less likely to boil over. This is much easier to do on a stovetop than in a microwave.
  3. Ingredients: Boil overs happen when starch (from oats, pasta, etc.) or protein (from milk, eggs, etc.) get into the water and create a mixture capable of foaming. Minimizing these ingredients can help, but you don't want to reduce the oats in your oatmeal. Instead, you can add other ingredients that interrupt the foaming action. Some other answers suggest using dried fruit or cinnamon for this, but my favorite is a bit of fat such as olive oil or butter.
  4. Mechanics: Try laying a wooden spoon or a few wooden skewers across the top of the pan. This helps when boiling potatoes or pasta, so it should help with oatmeal, too.

Out of these four things, the first two (vessel size and heat control) are going to make the biggest difference. The other two can help, but don't guarantee success.

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Try heating your water to a boiling without the oats. Place the amount of oats you want to eat in a microwave safe bowl, then pour the water on the oats until all oats are in the water and cover them for about 3 to 5 minutes. You not only will have an easier time washing the pot and you won't have it bubble over.

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When using a rice cooker to cook steel cut oats, simply leave the lid open while cooking. I use the brown rice setting on my rice cooker. And never stir until it’s done. It’s perfect every time!

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I am wondering if in some cases anyway, it's not something with the microwave. I say this because I have been making oatmeal in a bowl for years, the same way, and only for the past few months has it started to overflow, even at 80 percent power. I plan to start by giving the interior a thorough cleaning. Our machine is over ten years old, and the lights on the board have really faded anyway, so at the very least it might be a sign to shop for a new one.

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The key is the amount of liquid. If you have a real preference for mushy oatmeal then cinnamon and power reductions (although the latter not alone I've found) can help, but only adding a little over 1/2 liquid works perfectly. For me it makes a perfect consistency for adding some milk after and never overflows. I have it almost daily.

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Since I don't want to use a big bowl to cook a single portion of oatmeal, I find that I have to watch the oatmeal and stop the microwave and stir it every minute. I know that is a pain, since I want to put it in the microwave and then forget about it until my shower is over, but it is the only thing I've found that works.

I have read about slow cooker oats. You get the regular steel cut oats and let them slow cook overnight. I haven't tried it (because it also seems like a lot of work) but that could be a solution if the whole family eats oatmeal in the morning.

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I run a cube of margarine or butter around the inside edge of the bowl before cooking. Not enough to add calories. Also have set 1 paper towel on the turntable to catch any boil over if I don't want to do the butter thing. Has anyone tried laying a wooden spoon over the bowl as you do for stovetop pasta, soup etc.

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Just add some flaxseed. If you add a teaspoon to a tablespoon of flaxseed it has a nice nutty flavor plus more protein and it keeps your oatmeal from boiling over. You'll be pleasantly surprised

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