In a medium-sized jar or bowl, combine rolled oats, your choice of milk, and Greek yogurt, if using. Add maple syrup, cinnamon, and vanilla extract. Stir well until all ingredients are mixed and the oats are coated.

Seal the jar or cover the bowl with plastic wrap, then place it in the refrigerator. Allow oats to chill for at least 4 hours, preferably overnight.

The next morning, stir the oats and check consistency. If too thick, add a splash of milk to loosen them up.

Enjoy the oats cold or transfer to a microwave-safe bowl and heat for 30–60 seconds as desired. Garnish with toppings if desired.