1. Preheat oven to 350 degrees.
2. Lightly spoon flour into dry measuring cups, and level with a knife. Combine the flour, granulated sugar, toffee bits, brown sugar, and baking powder in a large bowl. Combine vegetable oil, vanilla, and eggs; add to flour mixture, stirring until well-blended (dough will be dry and crumbly). Turn the dough out onto a lightly floured surface, and knead lightly 7 to 8 times. Divide dough in half. Shape each portion into an 8-inch-long roll. Place rolls 6 inches apart on a baking sheet coated with cooking spray, and flatten each roll to 1-inch thickness.
3. Bake at 350 degrees for 35 minutes. Remove rolls from baking sheet; cool 10 minutes on a wire rack. Cut each roll diagonally into 15 (1/2-inch) slices. Place slices, cut sides down, on baking sheet. Reduce oven temperature to 325 degrees; bake 10 minutes. Turn cookies over; bake an additional 10 minutes (cookies will be slightly soft in center but will harden as they cool). Remove from baking sheet; cool completely on wire rack.