Preheat your oven to 350°F (175°C).

Grease an 8x8 inch baking dish with cooking spray or butter.

In a mixing bowl, combine the old-fashioned oats, baking powder, ground cinnamon, and chopped walnuts.

In another bowl, whisk together your milk and maple syrup, then add the eggs.

Pour the wet ingredients into the bowl with the dry ingredients and stir gently.

Fold in the chopped apples until evenly distributed.

Pour the combined mixture into the prepared baking dish and spread out evenly.

Bake in the oven for about 35-40 minutes or until lightly golden.

Cool for approximately 10 minutes before serving.