I have never heard of anyone cooking oats. However I know people cook barley.
Oats are only 11% protein, certainly not a protein source. And Oats have more crude fat than corn at 4% vs. 3.5%. I don't know what harm it would do to cook oats. Although there is more total energy in corn due to the carbs.
What has never been quantified is how much more digestible cooked grains are vs cracked or rolled. When grain from feces is analyzed from even whole grains, many University studies show that very little nutritive value is left in that grain. What cooked grains are for sure is more palatable and people swear they get better results by cooking grains.
Its like using barley to finish show cattle. I can't tell you WHY it does , but I like the results it gives me better than that of corn.