Oatmeal cookies contain all the health benefits of oatmeal, being high in vitamins, fiber and essential minerals. However, the FDA suggests limiting the amount of fats and sodium in the diet, the two components that makes oatmeal cookies worse for you than simply eating oatmeal.
Oatmeal itself provides health benefits. It is generally eaten in the morning due to the high level of dietary fiber, which is responsible for making you feel more "full" for longer. Furthermore, oats contain soluble fiber. According to the Mayo Clinic, soluble fiber is the type of fiber that can help lower blood cholesterol and glucose levels.