Preheat oven to 350°F. Lightly grease a 9x13 baking dish with cooking spray. Set aside.
In a large mixing bowl, mix cookie mix, oats, and butter using a hand mixer or stand mixer with a dough hook or whisk attachment until crumbly.
Cover a half sheet baking sheet with parchment paper and pour the cookie mixture out onto it, spreading it into an even layer.
Place the crumble in the freezer while you assemble the fruit layer.
Mix together the frozen blueberries and diced apples in the bottom of the casserole dish.