In a medium saucepan, combine the chopped apples, butter, brown sugar, flour, ground cinnamon, freshly grated nutmeg, water, and salt. Put the saucepan over medium heat and stir all the ingredients together. You'll want to allow this mixture to cook for about ten minutes, or until the apples soften and the sauce thickens. Once done, remove it from heat and let it cool as you tackle the next steps.

Set your oven to preheat at 350 degrees Fahrenheit. This is crucial since you want those apple bars to bake evenly. While the oven warms, grab your baking dish!

Grease a 9x13 inch baking dish with a non-stick cooking spray or butter to ensure your apple bars slide right out after baking. You don’t want your hard work sticking to the pan, do you?

In a large mixing bowl, whisk together the all-purpose flour, rolled oats, packed brown sugar, baking powder, and salt. This combination will create the delightful base and topping for your bars.

Using a fork or pastry cutter, add in the pieces of butter into the oat mixture. Work it in until you achieve a crumbly texture that sticks together when pinched between your fingers. Think of it as a mini workout for your arms!

Take half of your oat mixture and press it evenly into the bottom of the prepared baking dish. Make sure to pack it down firmly for a sturdy base.

Next, pour the cooled apple pie filling over your oat base. Spread it out evenly. This will create a beautiful layer of sweet, gooey goodness that will melt in your mouth.

Now, sprinkle the remaining oat mixture evenly on top of the apple filling. You want an even layer here to give each bite a perfect balance of sweet apples and crumbly oats.

Pop the baking dish into the preheated oven and let it bake for 30 to 40 minutes. You'll know it’s done when the top is golden brown and smells irresistible—like a warm hug on a plate.

Once the bars are baked to perfection, remove the dish from the oven and let it cool completely on a wire rack. If you can wait that long, slice it into 12 squares and serve. Any leftovers? Store them in an airtight container and enjoy later on!