What’s the Difference Between Quick Oats, Old Fashioned Oats, Instant Oats, and Steel Cut Oats?
Old Fashioned Oats (rolled oats)
Old fashioned oats are sometimes called rolled oats or old fashioned rolled oats. They are whole oats that are steamed and rolled flat into flakes. A recipe may rely on the larger size and longer cooking time of the Old Fashioned Oats. I would expect a more chewy texture with Old Fashioned Oats and they take longer to cook than Quick Oats.
Quick Oats (quick cooking oats)
The same as old fashioned oats except they are also cut into pieces. This allows them to cook quicker. Some recipes like No Bake Oatmeal Cookies rely on this shorter cooking time.
Instant Oats (Instant Oatmeal)
It’s the most processed of the types and cooks the fastest. It’s flatter and cut into more pieces than Quick Oats. You will typically see this in packets with other ingredients where you simply add hot water to make oatmeal.
Steel Cut Oats
These are cut into pieces. They are not rolled or steamed first and take longer to cook than old fashioned oats
I would avoid substituting one for the other and go with what a recipe specifies as using something different will probably affect the results especially the texture. If you do substitute one for the other keep in mind the texture will be different between each one of the cooking time will be different also.