1Combine first 4 ingredients in large bowl. Beat at medium speed 1-2 minutes. Press 1/2 of mixture into bottom of an ungreased 13x9 pan.
2Bake 10 minutes at 350. Remove from oven; sprinkle with chocolate chips and drizzle with milk. Sprinkle with remaining cake mix mixture. Bake at 350 for an additional 30 minutes. Let cool, cut into bars.