When people dream about eating oatmeal, they may be thinking about a particularly bland and dull life. It implies that the dreamer wants to avoid extravagance and outlandish activities perhaps to attain good health.
Some people might have a dream about oatmeal because they are craving it for breakfast. Eating oatmeal for breakfast can make you feel more grounded and less likely to be overly critical of yourself. Sometimes, people have dreams like these in order to get some relief from their stresses, such as work troubles or family problems.
Also, oatmeal in a dream represents a lack of creativity needed to think up fresh ideas, or simply something less bland than cardboard.