Add all ingredients (except for walnuts) to a bowl or mason jar and mix or shake well until thoroughly combined.
½ cup rolled oats, ½ cup milk, ½ cup plain Greek yogurt, ⅓ cup applesauce, 1 tablespoon chia seeds, 1 tablespoon maple syrup, 2 teaspoon cinnamon, ½ teaspoon vanilla extract, 1 pinch allspice