In a medium mixing bowl, whisk together the Greek yogurt, almond milk, vanilla protein powder, and cinnamon until the powder is fully incorporated.

Stir in the rolled oats and chia seeds until the dry ingredients are fully submerged.

Fold in half of the diced apples and half of the chopped walnuts into the oat mixture.

Divide the mixture evenly into two 16-ounce glass mason jars.

Top each jar with the remaining diced apples and walnuts.

Drizzle the maple syrup over the top layer of each jar.

Seal the jars with airtight lids and refrigerate for a minimum of 4 hours, preferably overnight, to allow the oats to hydrate and the mixture to thicken.