PB & J Overnight Oatmeal


Oats are one of the most beloved whole grains – in fact, when we surveyed American consumers in 2018, oats were the second most popular whole grain after whole wheat, and oatmeal was nearly the most popular whole grain food, coming in second only to whole grain bread. Despite this – or perhaps because of it – we get lots of questions from consumers who want to understand the differences between steel-cut, old-fashioned, and instant oats. 

Consider this your FAQ guide to all things oaty:

Which oats are whole grain?

We have good news for those of you oat-lovers seeking whole grain options. Oats are almost never refined, which means that no matter which box or canister you choose at the grocery store you’re pretty much guaranteed to be getting a whole grain product. Remember that a whole grain has all three of its original, edible parts – the bran layer, full of fiber and B vitamins; the germ, rich in healthy oils and other nutrients; and the starchy endosperm. When we say that a grain is refined, we mean some part of the original kernel has been removed. Often, in the case of refined flours, the germ and bran are stripped away leaving only the starchy endosperm. When it comes to oats, however, all three parts of the kernel remain regardless of the processed form you’re buying them in, which is why plain oats qualify as 100% whole grain. 

Ok then, what’s the difference between steel-cut oats and the instant variety? Is it a question of whether or not they’re processed?

Oat groats, from Grain Millers

The degree to which the oat kernel has been processed turns out to be the main distinguishing feature between the various types of oats. Here’s a breakdown of the most common forms of oats available to consumers:

  • Oat groats are fully intact oat kernels after they’ve been hulled and cleaned. These can be cooked much like you’d cook brown rice or wheat berries. They can take up to an hour to cook.
  • OatsSteelCutWGC.jpg
    Steel-cut oats, from Grain Millers
    Steel-cut oats (sometimes referred to as Irish or Scottish oats) are oat groats that have been chopped or sliced into smaller pieces. They have a chewy texture and nutty flavor and are most commonly used in porridge. They take about 30 minutes to cook.
  • Old-fashioned or rolled oats are oat groats that have been steamed and flattened. They can be cooked into oatmeal, baked into breads and muffins, or roasted into granola. They take about 5-10 minutes to cook. 
  • OatRollThickGrainMillers.img_assist_custom-199x139.jpg
    Rolled oats, from Grain Millers
    Instant oats are generally made from rolled oats that have been pre-cooked, dried, and then finely chopped. This is the type of oat you find in little packets, which often just require a little boiling water to cook. 

When we talk about processed foods, we’re talking about how much they have been changed from their original state in nature. Sometimes “processed foods” get a bad rap, but many people don’t realize that lots of common, healthy foods are processed. Yogurt, for example, was invented long ago as a way to keep milk edible for more than a few hours before refrigeration existed. Plain yogurt, made with just milk and natural bacteria (the “good” kind), is what we consider a minimally processed food. Of course, today you can find yogurts in your grocery store that are much more heavily processed, using pectin to thicken them rather than natural fermentation, and with lots of added sugars, artificial colors and flavorings, etc. 

While almost all grains have to be separated from their hull, cleaned, and cooked before eating – all forms of processing in the strictest sense of the word – we generally consider whole grains like brown rice, steel-cut oats, and quinoa to be “unprocessed.” A “lightly processed” whole grain would be something like whole grain pasta, or rolled oats, while a “heavily processed” whole grain would be something like instant oats with lots of added sugar, or a whole grain cookie. 

oatmeal with dried cranberries

Do the different types of oat processing have an impact on nutrition or digestion?

As we mentioned before, virtually all oats are whole, so no matter which type you choose, you can be confident you’re getting all the nutritional benefits of a whole grain. The nutrient content of your oats won’t fluctuate from one bowl (of old-fashioned oatmeal) to the next (of instant oatmeal). That doesn’t mean that our bodies will digest every bowl the same way, though.

Our bodies all need carbohydrates, but different carbohydrate choices can affect our bodies differently. As carbs are digested, they get broken down into blood sugar, which acts like fuel for our bodies. Carbs that break down slowly are said to have a low Glycemic Index. These are carbs that deliver energy to you bit by bit, as you need it. Carbs that break down quickly have a high Glycemic Index – they give you a big spike in blood sugar that overloads your body, followed by a crash that can leave you feel hungry and tired. In the world of grains, generally the more processed a grain is (whether it’s whole or not) the more likely it is to cause a blood sugar spike. 

In 2015, researchers from Quaker Oats tested the Glycemic Index of 72 oat products to understand how different types of oats affect blood sugar. They found that steel-cut oatmeal, large rolled oats, muesli, and granola produced a significantly lower glycemic response than quick-cooking and instant oatmeal. The scientists concluded that “smaller particle size and increased starch gelatinization appear to increase the glycemic response.”


We hope you’re feeling inspired to cook up a comforting pot of your favorite oats! Check out our recipes for some great, flavorful ideas. (Caroline)


Hey thanks for this. I work as a grocery cashier and get health questions from customers all the time. I'm also a big fan of instant oats for breakfast on work days. I will re-consider that based on the glycemic study.
Marty Glanville
There is an option that you don't have here. Sunrise Flour Mill has an oat cereal that is a rolled oat that has not been steamed before flattening.
Interesting -- this is not something we've heard of before. I wonder how they get the hard oat kernel to flatten without first softening it with steam.
Perhaps you know why the once popular and easily available oat bran is so hard to come by these days. Every grocery store including used to have their own brand with Wholefoods and the like selling it in bulk, but now I'm lucky to find it in any healthfood store.
Hi Teresa -- I'm not sure why this is. Oat bran is not a whole grain ingredient, so it's not one that we include on our whole grain ingredient sourcing pages, but I would guess you could order it online if you were having trouble finding it locally.
I love Oatmeal and have recently been disappointed to find out that weed killer is now used in some countries.
Hi Roxanne -- organic guidelines limits which pesticides/herbicides can be used during production, so seeking out organic oats might be a good option if you're concerned about how your oats have been grown.
Johnny Barrington
I love oatmeal but don't always have time to cook them. So I have always opted for the instant oatmeal. Unfortunately, I thought that meant they were processed and bad for me. I understand now that is not the case but I am a diabetic and I have noticed that my blood sugar spikes when I do eat instant oatmeal so I guess for me, specifically, instant oatmeal is not good. That is unfortunate as I am not familiar with cooking the other types of oats.
Hi Johnny -- That blood sugar spike you've observed is due to higher Glycemic Index of instant oats. They digest more quickly than longer-cooking oats, which causes your blood sugar to rise rapidly. You might try rolled oats or steel-cut oats as an alternative. They aren't hard to cook! Simply boil them in water (1 part oats to 2 parts water). Rolled oats take 5-10 minutes at a boil, and steel-cut oats require more like 20-30 minutes.
I have success cooking old-fashioned rolled oats in the microwave, using 1 part oats to 3 parts water, requiring only 3 minutes to cook. I use an extra-large cereal bowl because the oats may bubble up while cooking. This saves cleanup time, too.
Old fashioned oats are whole grain oats? So is whole grain oats is also a processed food?
Hi Jessa -- The word "processing" has come to have a bad connotation because many ultra-processed foods are less nutritious, however it's important to remember that the term "processing" actually refers to any step that is taken to transform a raw agricultural product into an edible food. All grains must undergo some processing before consumption. Most have a tough outer hull that must be removed. Then grains must be cooked, or soaked, or steamed, or ground into flour, etc. (or some combination of these) before they can be consumed. These are all forms of processing. Old-fashioned oats are grains that have gone through the processing steps of being hulled, steamed, and pressed in order to be edible. Processing in this case is a very good thing -- after all, trying to eat a raw oat groat would not be pleasant and might break a tooth!
Barry J White
Publix Old Fashioned Oats, 2 parts tap water to one part oats. 1 1/2 minutes on high in the microwave, done. Add a drop of milk. I add cinnamon, 1/2 a packet of Splenda and some raisins before cooking. If your gut is ever out of kilter, this will set it right.
Is the glycemic response different for 3 minute rolled oats different than for old fashion rolled oats? Thank you
Hi Jenifer – In general the faster the oat product cooks, the faster your body will digest it, and the faster it will make your blood sugar spike. I’m not aware of any studies that include 3-minute rolled oats, so I can’t tell you for sure, but I suspect that the 3-minute oats will have a higher Glycemic Index than standard rolled oats.
Inge Kohl
Sometimes I cook several servings of the old fashioned rolled oats (or steelcut) in a crockpot and then keep them in the fridge. I can then portion out what I need and reheat with a little more milk. Great to add chopped apples and cinnamon as well. My husband cooks his large portion of steelcut oats on the stove and then keeps it in the fridge like I do. Either way saves time and tastes great
Whole oats take 12 minutes in an Instant Pot and they are delicious!
I make a big batch of uncooked rolled oats from the bins mixed with ground nuts, shredded coconut, currants and wheat bran and then have about a quarter of a cup with milk for breakfast. Question: For my last batch, I whirred the oats a bit in the food processor to make them a bit smaller. Does that lessen their their whole grain level?
Sounds delicious! No, processing or grinding oats into smaller pieces does not lessen their whole grain level. So long as you are consuming all of the grain’s bran, germ, and endosperm without sifting out any of the components, you are consuming the whole grain.
Claudia Thompson
Once a week in the evening I cook 2 cups old fashioned oatmeal and a large diced apple in 4 cups water at a boil for about 3 minutes, then cover it and turn off the heat and leave it on the stove overnight. In the morning what I don’t eat then, I divide what now looks like a solid pudding into about 7 portions and freeze them in individual baggies for future use. When you’re ready to eat what you’ve made, just reheat or thaw in the microwave with a little milk or apple cider is also good.
I just bought some whole oats at a Korean/Asian store, but there's no English on the 5 lb. Package except the Nutritional info. Any suggestions on how to use these oats? I am unlikely to grind into flour. Toss into soup like barley? Cook slowly overnight as porridge? Any ideas or even recipes welcome.
Sounds great! You can view this blog post for more information on how to cook with all kinds of oats: https://wholegrainscouncil.org/whole-grains-101/whole-grains-101-orphan-pages-found/cooking-oats And, check out this recipe for whole oats: https://wholegrainscouncil.org/recipes/miso-kale-power-bowl
Margaret McLane
Just as important to the "Whole" aspect / nutrient density of the grain, is the health of the soil in which it is grown. (We just finished the internationally attended "Soil Regen Summit", sponsored by the Soil Foodweb School). Unfortunately, there is no information easily available on this, to the average consumer, that I know of. What one CAN do is 1. become knowledgeable of this issue, 2. research the sources of your grains, and 3. Support those businesses that practice soil regenerative agriculture. I do know that there are farmers that are growing, on a smaller scale, here for example, in California, many grains. There is a bakery in LA that sources their flours from these / this particular farmer, for the quality and taste, just for their breads.
Stella Lopez
After reading your article, I will be changing from instant oatmeal to steel cut. I can eat it 3 times a day. This is my daily recipe: Stir the cooked oatmeal, in a bowl, sliced red grapes, blueberries, 1/2 sliced banana, chopped walnuts, 1tsp chia seeds & 2 good Tsp vanilla nonfat yogurt! I never get tired of it!

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