Prepare brownie mix as directed on package; spread in greased 13x9-inch baking pan.

Mix cream cheese, sugar and vanilla in medium bowl with electric mixer on medium speed until well blended. Add egg; mix until blended. Pour over brownie mixture; cut through batter with knife several times for marble effect. Sprinkle with chips.

Bake at 350°F for 35 to 40 minutes or until cream cheese mixture is lightly browned. Cool in pan on wire rack. Cut into squares.