Preheat the oven to 350 degrees F. Line a square baking pan with parchment paper and set aside.
Using a food processor, pulse the oats, flour, sugar, baking powder, cinnamon, salt, egg, and coconut oil until it forms a crumbly sticky meal.
Set aside 1/3 of the mixture to use for the topping.
Add the dough into the prepared baking pan and press evenly into the bottom.
In a small saucepan over medium heat, add the diced apples, vanilla extract, lemon juice, nutmeg, water, and maple syrup until heated and the sauce is warm.
Stir the chia seeds into the apple mixture and cook for an additional 5 minutes. Pour the mixture onto the dough in the baking dish.
Sprinkle the topping that you set aside on top of the apple mixture evenly.
Place into the oven and bake for 30 minutes or until lightly browned.
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.