Preheat oven to 350°.
Microwave butter and chocolate in a small bowl at HIGH 35 seconds or until chocolate begins to melt. Stir chocolate mixture until smooth.
Beat chocolate mixture, sugar, and next 3 ingredients in a large bowl until smooth.
Combine oats, flour, baking powder, and salt; add to butter mixture, stirring just until blended. Drop by rounded teaspoonfuls 2 inches apart onto baking sheets coated with cooking spray.
Bake at 350° for 8 to 9 minutes or until cookie centers are almost done. Cool 5 minutes on pans. Remove from pans; cool completely on wire racks.