Spray parchment-lined half-sheet pan with cooking spray.
Combine dry ingredients in bowl of mixer fitted with paddle attachment. Add combined liquid ingredients, all at once; beat on low speed just until dry ingredients are moistened. Pour into prepared pan.
Bake in 350°F standard oven 25 to 30 min. or until wooden pick inserted in center comes out clean. Cool 15 min. before cutting into 2-inch squares to serve.