Combine all of the ingredients except for the banana and peanut butter into a container.
Place the container in the fridge overnight.
Remove from the fridge the next morning and top with banana and peanut butter.
To make warm oatmeal
Add all of the ingredients except for the peanut butter to a microwave-safe bowl. Heat the bowl in the microwave until the oatmeal is fully cooked (~ 3 minutes).