Cook the oats according to the package directions, either in the microwave or on the stove. You can use water or milk as the liquid.
Let the cooked oatmeal cool slightly, and then transfer to a blender and process, adding an extra couple of tablespoons of water or milk as needed to reach a smooth consistency.
Transfer to a small bowl and serve immediately, or store until ready to use. Store in an airtight container in the refrigerator for 3 to 5 days or in the freezer for 4 to 6 months. The oatmeal will continue to thicken as it cools—and after it is stored—so you might need to mix in some additional water or milk to help thin it out again.