Preheat the oven to 350 degrees F. Grease a 9-inch cake pan, line it with a round of parchment paper cut to fit, and grease again.
Add the butter, applesauce, egg, and vanilla to a medium bowl. Beat with an electric mixer for about 1 minute.
Add the sugars and beat on medium for an additional minute.
Gently fold in the flour, oats, coconut, baking soda, salt, and chocolate chips.
Gently press mixture into the bottom of the prepared pan and press with a spoon to even out to the edges.
Bake for 24-26 minutes or until golden brown around the edges and just set in the center.
Let cool for at least 15 minutes before transferring to a cutting board, slicing into wedges, and serving.
Store any leftovers in an airtight container for up to 4 days.