Begin the recipe by preheating the oven to 350 degrees F. and line a square baking pan with parchment paper and set aside.
Using a food processor, pulse together 1 cup old fashioned oats, 1 cup all-purpose flour, ¼ cup brown sugar, 1 teaspoon baking powder, 1 teaspoon ground cinnamon, ¼ teaspoon salt, 1 large egg, and ½ cup melted coconut oil until it forms a crumbly but sticky mixture.
Set aside ⅓ of the mixture to use for the topping. Add the rest of the mixture into the prepared parchment-lined baking pan and press evenly into the bottom of the pan.
In a small saucepan over medium heat, add the 2 cups diced apples, 1 teaspoon vanilla extract, 1 tablespoon lemon juice, 1 teaspoon ground nutmeg, 2 tablespoons water, and 1 tablespoon maple syrup until heated and the sauce is warm.
Stir 1 tablespoon chia seeds into the apple mixture and cook for an additional 5 minutes. Pour the mixture onto the crust mixture in the baking dish and spread in an even layer.
Sprinkle the reserved ⅓ topping that you set aside on top of the apple mixture evenly.
Place into the oven and bake for 30 minutes or until the top has lightly browned.
Carefully remove from the oven and allow the bars to cool in the baking dish for 10 minutes before transferring to a cooling rack to cool completely. Slice into bars and serve.
Store the extra in an airtight container for up to 5 days at room temperature or in the refrigerator.