Preheat the oven to 350°F (175°C) and line a large baking sheet with parchment paper.
Mix the dry ingredients. In a large bowl, stir together the rolled oats, oat flour, cinnamon, baking powder, and salt.
Whisk the wet ingredients. In a separate bowl, whisk the egg, applesauce, maple syrup, melted coconut oil, and vanilla until smooth.
Combine. Pour the wet mixture into the dry ingredients and stir until evenly moistened.
Fold in the chopped apple, nuts, raisins, and chia seeds (if using). The dough will be thick and sticky.
Rest the dough for 5 minutes. This lets the oats hydrate for a better, chewier texture.
Scoop the cookies. Use a heaping tablespoon or cookie scoop to portion 12–14 mounds onto the baking sheet. Flatten gently with damp fingers; these don’t spread much.
Bake for 13–16 minutes, until the edges are set and lightly golden. The centers should be just firm to the touch.
Cool completely. Let the cookies rest on the sheet for 5 minutes, then move to a wire rack.
They firm up as they cool.
Enjoy now or store for later. They’re great warm, but even better the next day as the flavors meld.