Whisk together all ingredients in a medium-sized mixing bowl. Spoon into a jar with a tight-fitting lid.
Close and refrigerate for at least 4 hours, but preferably overnight before eating.
Video
Notes
Most of my overnight oats recipes can be made days or even a week in advance, but I only recommend making this recipe the night before you eat, or the enzymes in fresh pineapple will make these oats bitter. If you want to make this further in advance, use canned pineapple in place of fresh, up to 7 days ahead of time.