Oatmeal. Rolled is already steamed, so it is already cooked. I'm in the US. I buy from Azure Standard in 25 or 50 lbs bags. They have organic oats. I keep them in the large tupperware container I used to keep flour in, and 3 and 5 gallon food grade buckets.
I'm a fan of steel cut oats. I use oats and water, ratio of 1:3 or 1:4 or something in between. Bring it to a boil, then turn off and let it sit a half hour, put in quart containers which refrigerate or freeze fine. I just warm it up a cooked cup of them the next day with cranberry/orange cooked puree, flax/chia, cinnamon, honey.
Groats, I use the same ratio of 1:3 or 1:4 with water, bring to a boil, and then stir for a while, then after about a half hour it is done. Package as above. They are mushier and more like barley in my opinion. I still eat them but may not buy them again.
Mr feather is a thick rolled oats fan. He takes a little more than 1/2 cup of them, with water, heats it in the microwaves, twice, stirring in the middle. He added either blueberries or raisins, adds flax/chia, cinnamon, and honey. He will sometimes add a home canned fruit puree instead of berries or raisins. When he watched the Dr Greger video on how blueberries make you smarter, he began telling me each day he had blueberries that I needed to watch out because his smartness was increasing.
He's a funny man!
We make oatmeal cookies all the time so that we can substitute those for a breakfast if we are running out early in the morning, or for a snack to keep in the truck.
There is also a savory oatmeal I like for breakfast. Oats, little broccoli trees, some garlic, and some miso dissolved in water. Sometimes I use chopped stems of broccoli, either way it is satisfying and delicious.