1. Preheat oven to 350°.
2. Line bottom and sides of a 13 x 9–inch baking pan with foil; coat foil with cooking spray, and set aside.
3. Weigh or lightly spoon flour into dry measuring cups; level with a knife. Combine flour, cornstarch, and salt in a large bowl; stir with a whisk.
4. Place butter in a medium bowl; beat with a mixer at medium speed 2 minutes or until light and fluffy. Add oil; beat with a mixer at medium speed 3 minutes or until well blended. Gradually add sugar, beating well. Scrape seeds from vanilla bean, and add seeds to butter mixture; discard bean. Add flour mixture, beating at low speed just until blended. Spoon dough into prepared pan. Place a sheet of heavy-duty plastic wrap over dough; press to an even thickness. Discard plastic wrap. Bake at 350° for 30 minutes or until edges are lightly browned. Cool in pan 5 minutes on a wire rack; cut into 32 pieces. Carefully lift foil from pan; cool squares completely on a wire rack.