Combine first three ingredients is large bowl; set aside. Bring brown sugar and honey to a boil in a small saucepan over medium-high heat, stirring constantly; remove from heat. Stir in peanut butter and vanilla until blended. Pour peanut butter mixture over cereal mixture, stirring until coated; let stand 10 minutes. Press mixture into a 13X9" pan; cool in pan on a wire rack. Cut into bars, and wrap individually with plastic wrap.
