In a large bowl, stir together your Greek yogurt, milk, pumpkin puree, vanilla, maple syrup or raw honey until well combined.
Stir in your oats, chia seeds, and pumpkin pie spice.
Pour into a large container with a lid (or 4 separate smaller containers) and place in the fridge (sealed tight) for 6 hours or overnight.
Glass canning jars work really well for this.
Once you're ready to eat, give your oats a good stir.
Garnish with chopped pecans, walnuts, pumpkin seeds, or any topping of your choice.
Your oatmeal will stay good in a sealed container in the refrigerator for 3-4 days.