In a large bowl, whisk together the rolled oats, vanilla protein powder, chia seeds, and ground cinnamon until well combined.
Incorporate the mashed banana, Greek yogurt, almond milk, vanilla extract, and maple syrup into the dry base.
Stir the mixture vigorously to ensure all protein powder is dissolved and the texture is uniform.
Divide the contents equally into two 16-ounce mason jars or airtight containers.
Seal the containers tightly and place in the refrigerator for a minimum of 4 hours, or up to 8 hours for optimal texture.
Serve chilled, topped with fresh banana slices or crushed graham crackers if desired.