Preheat the oven to 350°F (175°C).
In a large bowl, mix the rolled oats, whole wheat flour, baking powder, cinnamon, and salt.
In another bowl, whisk together the melted coconut oil, honey (or maple syrup), and vanilla extract.
Pour the wet ingredients into the dry ingredients and mix until just combined.
Fold in the diced apples and nuts (if using).
Scoop tablespoon-sized portions of dough onto a parchment-lined baking sheet.
Bake for 12-15 minutes, or until the edges are golden brown.
Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack.
Store the cookies in an airtight container.