Preheat your oven to 350°F (175°C) and line a 9x13-inch baking pan with parchment paper.
In a large bowl, mix melted butter, brown sugar, flour, oats, baking soda, and salt until crumbly.
Press about 2/3 of the mixture into the bottom of the prepared pan.
Spread the apple pie filling evenly on top, then sprinkle with cinnamon.
Crumble the remaining oat mixture over the apples.
Bake for 30–35 minutes or until the top is golden brown and your kitchen smells like heaven.
Cool completely before slicing into bars—or don’t, and embrace the warm gooey chaos!