Place an oven rack in the center of the oven. Preheat the oven to 400 degrees F. Liberally spray an 8-by-8-inch glass baking dish with vegetable oil cooking spray. Set aside.
In a medium bowl, mix together the cornbread mix, buttermilk, melted butter, eggs, olives, scallions, and cheese until the mixture forms a thick, lumpy batter. Using a spatula spread the batter into the prepared baking dish. Bake until golden brown, 25 to 30 minutes. Allow the cornbread to cool in the pan for 15 minutes. Cut into 1 1/2-inch squares and serve.
Cook's Note: To remove the cooked cornbread easily from the baking dish, first line the bottom and sides with 2 pieces of parchment paper, each 7 inches wide and 15 inches long, allowing the excess parchment paper to overhang the sides. When cooked and cooled, use the excess parchment paper as handles to remove the cornbread from the pan. Peel away the parchment paper and cut into squares.