As long as it's oatmeal with nothing added, I don't see why it would be a problem. Is it just oatmeal that has been ground up? I buy rolled oats in bulk and then run them through a coffee grinder until they are basically powder before I use them in soaps. Oh wait - I think I know what you're talking about - the baby's first solids type of oatmeal that you buy in a box and add breast milk or formula? Hmmm, I don't know about that. It seems like it would just dissolve or turn to pudding - that's what it always did when I added liquid and fed it to my kids!