In a microwave-safe bowl, place the oats, brown sugar, cinnamon (if using), and a pinch of salt.
Pour the milk or water into the bowl and mix to combine. Make sure to use a large enough bowl for the oats to cook.
Cook:
Microwave on high for 90 seconds, making sure to stop after a minute to stir so the oatmeal doesn't bubble over. Cook for an additional 30 seconds if necessary.
Remove the oatmeal from the microwave and serve as is or topped with your favorite fruit or toppings.