PREHEAT oven to 350°F. Prepare cake mix as directed on package, substituting brewed coffee for the water. Spread evenly into 15x10x1-inch baking pan. Bake 20 minutes.
MEANWHILE, mix remaining dry ingredients in large bowl. Cut in butter with pastry blender or 2 forks until mixture resembles coarse crumbs; sprinkle evenly over partially baked cake.
BAKE an additional 20 minutes or until toothpick inserted in center comes out clean. Cool. Cut into 24 squares to serve.