Add oats, quinoa flakes, chia seeds, and cinnamon to a large bowl. Stir to combine.
Whisk together milk and applesauce (maple syrup optional here!). Stir into oat mixture and cover with plastic wrap. Refrigerate mixture overnight.
For the apple pie filling: peel and dice apples. Add apples to a small saucepan along with the cinnamon, syrup, and water; bring to a boil.
Reduce to a simmer and cook until mixture begins to thicken, about 5 minutes. Remove from heat and stir in chia seeds. Allow the mixture to cool for 5-10 minutes before assembling the oats.
Layer oats and filling into cups for a parfait, or simply spoon the oats into bowls and top with filling. Enjoy!