PREPARATION:

1. Combine flour, baking powder and salt in small bowl; set aside. Beat butter and sugar in large bowl with electric mixer at medium speed until light and fluffy. Add egg and vanilla; beat well. Gradually add flour mixture. Beat at low speed. Stir in oats.
2. Place chocolate chips in 1-cup glass measure. Microwave on HIGH about 2 minutes or until melted, stirring after 1-1/2 minutes. Divide cookie dough in half. Add melted chocolate to one half; mix well.
3. Roll out each half of dough between 2 sheets of waxed paper into 15X10-inch rectangle. Remove waxed paper from top of each rectangle.
4. Place chocolate dough over plain dough; remove bottom sheet of waxed paper from bottom of chocolate dough. Starting at long side, tightly roll up dough jelly-roll fashion, removing waxed paper as you roll. Wrap dough in plastic wrap; refrigerate at least 2 hours or up to 24 hours.
5. Preheat oven to 350°F. Lightly grease cookie sheets; set aside.
6. Unwrap log. Cut dough into 1/4-inch slices. Place 3 inches apart on prepared cookie sheets. Bake 10 to 12 minutes or until set. Remove cookies to wire racks; cool completely. Store tightly covered at room temperature or freeze up to 3 months.