because it is more processed. For some folks who aren't stable or who have really bad D, the IF in oatmeal (which is about equal to the amount of) SFcan be too much. Here are some previous board discussions about that: About oatmeal About oatmeal 2 Oatmeal Poll
I also eat Quaker Instant Oatmeal (original/plain and Cinnamon Roll), which come in the individual packets. Sometimes I add walnuts before I microwave it; the walnuts are so good with the Cinnamon Roll flavor!
I think most oatmeal is safe for most people with IBS as long as you watch out for added dairy, HFCS, and sugar substitutes (sorbitol etc).