1 (1 lb. 2.25 oz.) box yellow cake mix
14 tbsp. (1 3/4 sticks) chilled unsalted butter, cut into pieces
3/4 c. packed dark brown sugar
1/2 c. old-fashioned oats
1 tsp. ground cinnamon
1 1/2 c. chopped pecans
2 (1 lb.) bags frozen unsweetened blueberries
1 (20 oz.) can crushed pineapple in heavy syrup

Preheat oven to 350°F. Butter 13 x 9 x 2-inch glass baking dish. Combine cake mix, butter, 1/4 cup sugar, oats and cinnamon in large bowl. Rub together in fingertips until mixture resembles coarse meal and holds together in large moist clumps. Mix in pecans. Mix frozen blueberries, pineapple with syrup and remaining 1/2 cup sugar in prepared dish. Cover fruit with cake mix topping.

Bake crumble until fruit is bubbling thickly and topping is brown and crisp, about 1 hour. Let stand 15 minutes.