When it comes to cooked oatmeal, the general rule of thumb is to consume it within a few hours of cooking. But, let's be real, who hasn't left their oatmeal out for a bit too long? It's not the end of the world, but it's not ideal either. Bacteria can start to grow, making your oatmeal go from yummy to yucky.
Now, if you're talking about uncooked oatmeal, that's a different story. It can sit out for a pretty long time, but it's still important to store it properly. You don't want any pests getting into your oatmeal, do you? That would be a total bummer.