There are a few different ways that you can make oatmeal thicker. One way is to add more oats to the recipe. This will make the oatmeal more dense and thick. Another way is to cook the oats for a longer period of time. This will also make them more dense and thick. Finally, you can add other ingredients to the oatmeal that will help thicken it up such as chia seeds, flaxseed meal, or ground nuts. All of these options will help create a thicker bowl of oatmeal that is more filling and satisfying