Combine ingredients: In a mason jar or bowl, mix rolled oats, pumpkin purée, milk, chia seeds, sweetener, pumpkin spice, and vanilla extract.
Stir well: Make sure everything is evenly combined.
Refrigerate overnight: Cover and let the oats soak for at least 4 hours or ideally overnight.
Stir before serving: Add a splash of milk if the oats are too thick.
Top and enjoy: Add your favorite toppings like chopped pecans, granola, or a drizzle of nut butter.