Meanwhile, in medium bowl, make cookie dough as directed on pouch for drop cookies. Stir in 1 cup of the candies. Drop half of the cookie dough mixture in chunks on top of baked brownie layer; add half of the Oreo™ pieces. Repeat with remaining cookie dough and Oreo™ pieces. With back of spoon or offset metal spatula, gently press cookie dough together to form even layer. Top with remaining 1/4 cup candies, pressing gently into cookie dough.