Preheat oven to 375 degrees.
Line a 9 x 13 baking dish with parchment paper or grease with cooking spray.
Mix cake mix and oats in a large bowl.
Add melted butter, stir until crumbly.
Press down half the crumbs onto the bottom of the pan.
Carefully spread blueberry pie filling over the crumb crust.
Spread remaining crumbs over pie filling and press down gently.
Bake for 18 to 23 minutes or until very lightly golden brown.
Eat warm or cool, cut into bars, and serve.