Yes — plain cooked oatmeal.
Plain cooked oatmeal is a good source of soluble fiber and gentle on digestion. Serve it plain — no sugar, raisins (toxic!), or flavored packets.
Enjoy — this is a safe treat in sensible portions. Introduce any new food gradually and watch for individual sensitivities, just like with people.
Get the printable list of the 30 most dangerous foods for dogs.