Preheat oven to 300°.
Place first 5 ingredients in a large bowl; beat with a mixer at medium speed until well blended. Lightly spoon flour into dry measuring cups; level with a knife. Combine flour, baking soda, and salt; gradually add to sugar mixture, beating until well blended. Stir in chocolate.
Turn dough out onto a baking sheet coated with cooking spray. Shape dough into 2 (12-inch-long) rolls; pat to 2 1/2-inch width.
Bake at 300° for 35 minutes. Remove rolls from baking sheet; cool 10 minutes on a wire rack.
Cut rolls diagonally into 24 (1/2-inch) slices. Place, cut sides down, on baking sheet. Bake at 300° for 10 to 12 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.