Add the oats, milk, maple syrup, vanilla extract, and a tiny pinch of salt to a sealable container (e.g., Weck jar, Mason jar).
Stir to combine. Close the jar airtightly and place it in the refrigerator overnight (or for at least 4 to 6 hours).
The next day, stir in the yogurt and add your favorite toppings. I used thawed raspberries, mixed with a dash of cinnamon.
Video
Notes
The best oats to use for overnight oats are old-fashioned rolled oats as they will soften but still keep a firm texture. You can use quick-cooking oats, also known as thin rolled oats (NOT instant oats), which provide a softer, gooier texture. *I used quick-cooking oats for this recipe because they are the only gluten-free certified ones I could find in my area.
The milk you chose largely determines the flavor of your oats. You can go for more neutral milk such as soy milk, rice milk or oat milk, or you can choose nutty kinds of milk such as almond milk. Coconut milk provides a more tropical flavor. I highly recommend varying the milk depending on your toppings (see variation ideas above).