Preheat oven to 350℉. Lightly spritz baking dish with nonstick cooking spray.
In a large bowl, add 2⅔ cups sifted purpose flour, 2 tablespoons baking powder, 4 teaspoons sugar, and 1 teaspoon salt. Whisk well.
Using a pastry blender add 10 tablespoons cold butter. Cut butter into flour mixture until it is the consistency of small lentils. Set aside.
In a separate bowl toss 1½ quarts of blueberries and 1 teaspoon orange zest. Spread over bottom of baking dish and drizzle with ½ cup orange juice.
In a separate bowl, add 2⅔ cups biscuit mix and ¾ cup sugar. Mix well and sprinkle mixture evenly over top of blueberries.
Drizzle ¾ cup melted butter evenly and scatter with 1 cup chopped pecans.
Bake 45 to 50 minutes or until lightly browned.
Garnish with 1 cup whipped heavy cream or a pint of vanilla ice cream. Serve at once.