How to Make Oatmeal: Ratios, Cook Times & Overnight Oats

Hello lovelies,

oatmeal is the breakfast that lands on our table most often, and also the one I get the most questions about: How much water? How long? Rolled or quick? And why does mine turn out either glue or soup?

The answer is almost always the same: it comes down to the ratio and the type of oats, not the recipe. So this is not another oatmeal recipe with toppings. It is the numbers behind it, written down properly once, for every kind of oats you will find on the shelf, plus overnight oats, Swiss Bircher muesli and the recipes where we put all of it to work.

Which oats should you use for oatmeal?

Quick-cooking oats make the creamiest oatmeal, old-fashioned rolled oats make the chewiest, and instant oats need no stove at all. All three come from the same grain; the difference is how long the kernel was steamed and how thin it was rolled.

The Harvard T.H. Chan School of Public Health sorts oats by processing: whole groats, then steel-cut, then rolled flakes, and finally the thin quick and instant flakes. The finer the flake, the faster it absorbs liquid and the softer the bowl. They are all whole grain: only the inedible hull is removed from oats, and germ, bran and endosperm stay in the kernel, even in quick oats. Nutritionally the types barely differ; where they do differ is how fast the body digests them, with steel-cut and thick rolled oats keeping you full longer than instant.

Labels vary: old-fashioned means thick rolled flakes, quick or quick-cooking means thinner rolled flakes, instant means very thin flakes that are often pre-cooked and sometimes sweetened, and steel-cut oats, also sold as Irish oats, are the whole groat chopped into pieces. Oat bran is the outer layer of the kernel with a lot of fiber and belongs more as a spoonful on top of a finished bowl than in the pot.

What is the ratio of oats to liquid?

For creamy oatmeal that holds its shape, use ½ cup (45 g) rolled oats to 1 cup (240 ml) liquid; for a softer bowl use 1¼ cups. By weight that is roughly 1:5, which is why recipes that measure in cups and recipes that measure in grams seem to disagree: cups measure volume, and ½ cup of oats weighs far less than ½ cup of water.

More important than the exact number is settling it once for the oats you buy. Quick oats bind faster and want the lower amount, old-fashioned oats swell more slowly and take the extra quarter cup. If you like your oatmeal spoonable, stay at the low end and pour a splash of cold plant milk over the bowl when serving. That contrast of warm porridge and cool milk matters more at our table than any topping. Half a cup is a normal adult serving, ⅓ cup is plenty for a child; when you cook for 2 or 4 the ratio stays the same and only the cook time stretches by a minute or two.

As for the liquid: water gives the purest oat flavor and scorches the least, plant milk makes it creamier and sweeter, and half water, half milk is the compromise most people land on. Oat milk doubles down on the nutty side, soy milk brings protein, coconut milk turns breakfast into dessert; if you use canned coconut milk, thin it 1:1 with water or the bowl turns heavy. And the pinch of salt goes in every time, even in sweet oatmeal: it lifts the oat flavor without tasting salty.

How long does oatmeal take to cook?

Quick-cooking oats take 3 to 5 minutes, old-fashioned rolled oats 8 to 10, and both finish over low heat with occasional stirring, never on a rolling boil. Oatmeal is done when the liquid is absorbed and a spoon leaves a short trail that slowly closes again.

The order that always works for us: oats, liquid and salt go into the cold pot together, come up to a boil once, then straight down to low heat. Pour oats into boiling liquid and you get lumps; keep boiling hard and you get a scorched pot. You do not have to stir constantly, but run the spoon across the bottom every 30 seconds or so.

Let it stand 1 to 2 minutes off the heat: oatmeal keeps thickening as it cools, and what looked perfect in the pot is often too stiff in the bowl. Take it off a little looser and let it set. The same ratio works in the microwave in a tall bowl: 2 to 3 minutes at 800 watts, one stir in between, then a minute to stand, and the bowl has to be tall because oatmeal climbs as it boils. Steel-cut oats are the outlier at 20 to 25 minutes; in return they taste nutty and stay distinct, and because they take that long, we cook them on Sunday for 3 days at a time.

These three warm bowls are the ones that show up most often at our house:

Creamy Apple Cinnamon Porridge with Caramelised Apples

Creamy porridge with cashew milk

Chocolate Banana Porridge with Caramelized Banana

Overnight oats: ratio, soaking time and shelf life

For overnight oats, stir ½ cup (45 g) quick or rolled oats with ½ cup (120 ml) liquid and let them soak in the fridge for at least 4 hours, ideally overnight. That is about 1:1 by volume, far less liquid than cooked oatmeal, because nothing evaporates in the cold.

Old-fashioned oats work too, but they need the full night and stay chewier. If you add a spoonful of chia seeds, count on about 3 tablespoons (50 ml) of extra liquid per tablespoon of chia, because chia swells hard; the exact numbers are in my guide on how to use chia seeds. Swapping part of the milk for yogurt or plant yogurt makes the oats thicker and creamier.

Bircher muesli is the Swiss ancestor of overnight oats: oats soaked overnight, freshly grated apple stirred in the next morning, nuts, a squeeze of lemon. We eat it all year, in fall with pear and toasted nut butter instead of berries. Soaked oats keep for 2 days in our fridge; toppings like banana or berries go in the morning of, otherwise they turn brown or watery overnight. For the office or school, mix them right in a screw-top jar: oats and liquid at night, toppings and lid in the morning, and the jar survives the commute as well as the fridge at work.

Apple-cinnamon Overnight Oats 2 ways

Chocolate overnight oats

Autumnal Bircher Muesli

Are oats gluten-free?

Oats are naturally gluten-free, but conventional oats can be cross-contaminated with wheat, barley or rye during growing and processing, so only oats labeled gluten-free are an option for people with celiac disease. That is how the Mayo Clinic puts it, and it is the point where many websites stop too early.

The contamination happens in the field, in transport and at the mill, where oats run through the same equipment as wheat. Oats labeled gluten-free have been grown and processed to avoid that. There is a second caveat: some people with celiac disease react to avenin, a protein in the oat itself, so whether oats belong in a gluten-free diet at all is a question for your healthcare professional, not for a food blog.

For everyone else this is a footnote. If you want a bowl without oats, whether out of caution or for variety, millet flakes are a grain that is naturally gluten-free and cooks on the same principle; they turn almost as fine as cream of wheat. Whole quinoa goes the same route, stays more distinct and tastes nutty; our quinoa porridge mixes it with rolled oats, and with oats labeled gluten-free or with the oats left out it becomes gluten-free too.

Millet porridge with orange

Coconut Quinoa Porridge with Tropical Fruit

CHOCOLATE ORANGE GRANOLA

What is in oats?

Per 100 g (3.5 oz), dry oats deliver 379 calories, 13.2 g of protein, 6.5 g of fat, 67.7 g of carbohydrates and 10.1 g of fiber in the USDA database. A ½-cup serving of about 45 g puts roughly 6 g of protein and 4.5 g of fiber in the bowl before a single topping.

The best-known component is beta-glucan, a soluble fiber that forms the silky body you either love or hate about oatmeal. The European food safety authority EFSA reviewed the evidence and confirmed a cause-and-effect relationship between oat beta-glucan and lower LDL cholesterol, with the effect established at an intake of 3 g of beta-glucan per day. That is a vetted statement, not a miracle claim, and it explains why oats are the one breakfast grain that food authorities name so explicitly.

Oats also bring iron and magnesium in amounts that are notable for a grain. If you build breakfast around protein, pair oats with soy milk, nuts or seeds; how that works without powders is in my post on high-protein vegan breakfast ideas. A tablespoon of nut butter or a handful of pumpkin seeds shifts the numbers of a bowl more than any powder does. And where oats sit in the bigger fiber picture is in my guide to high-fiber foods for every day.

Can you make savory oatmeal?

Yes, oatmeal works savory: vegetable broth instead of milk, an extra pinch of salt, and on top anything you would put on a bowl. The ratio stays the same, ½ cup oats to 1 to 1¼ cups liquid; only the direction of the seasoning flips.

Old-fashioned oats suit this better than quick oats, because savory oatmeal should lean toward risotto rather than porridge. At our house it gets sautéed mushrooms, spinach, a spoonful of miso or soy sauce and toasted sesame seeds, and in fall yesterday's roasted vegetables. If you want protein on top, add crispy fried tofu, the way it is described in my vegan tofu recipes from crispy to creamy.

Savory oatmeal is also the most elegant way to use up leftovers: half a cup of broth, a bit of vegetable, a handful of oats, and three odds and ends become a warm dinner in 10 minutes. Across Asia that has been everyday food for centuries; rice congee works on exactly the same principle.

The 5 most common oatmeal mistakes

Almost every failed bowl of oatmeal comes down to one of 5 mistakes, and none of them has anything to do with the recipe.

1. High heat to the end. Oatmeal scorches the moment the liquid is absorbed. Drop to low right after it boils.

2. Oats into boiling liquid. That gives you lumps on the outside and raw flakes inside. Everything goes into the cold pot together.

3. The wrong type. Instant oats for a chewy bowl or old-fashioned oats for a 3-minute breakfast both end in frustration. The table above decides.

4. No salt. Without a pinch of salt oatmeal tastes flat, no matter how much cinnamon is on top.

5. Toppings too early. Banana, berries and nuts go on the finished bowl, not in the pot. Otherwise the fruit browns and the nuts go soft.

Get these 5 right and you no longer need a recipe, just the table above and an eye on the pot.

How do you make oatmeal ahead for the week?

Cooked oatmeal keeps in a sealed container in the fridge, and at our house it is eaten within 2 days; a splash of liquid brings it back to creamy in 2 minutes. Cooking ahead is what makes steel-cut oats a weekday option at all.

Here is how it runs for us: on Sunday I cook a big pot of steel-cut or old-fashioned oats with a little more liquid than usual, portion it into jars, and put a jar of Bircher muesli for Monday next to it. On weekday mornings a jar goes into the pot with a splash of oat milk, 2 minutes of stirring, done. Both my girls eat it without a word of protest, in Switzerland just as they do now in Bali, where six in the morning is still cool enough for a warm bowl.

The rule for cooking ahead is the same as for all make-ahead food: cool it quickly outside the fridge, then chill it, and do not let it sit longer than 2 days. Reheat on the stove or in the microwave, always with a splash of liquid and a good stir, because oatmeal sets almost solid when cold. The full rundown of how long meal prep really lasts has its own post.

Oats are not only breakfast, either. They make the crumble on my plum cake with oat crumbles crisp without any flour. They also bind patties, granola and bars without a single egg. The banana chocolate granola bars go into the kids' lunchboxes at our house because they still hold together on day two.

Lovelies, if you remember only one number, make it this one: ½ cup oats, 1 cup liquid, a pinch of salt, low heat. Everything else is variation, and the prettiest one is the apple cinnamon porridge with caramelized apples that starts fall mornings at our house.

Tell me in the comments: do you like your oatmeal creamy or chewy, and what goes on top?

Yours, Verena

Recipes to try

Chunky Granola with chestnut puree

Blueberry granola bars

Chocolate Granola

Apple muesli buns