In many severe maneuvers, the driver-controller interaction seems necessary for maintaining a stable vehicle. This paper introduces a novel cooperative direct yaw control (DYC) design for optimal vehicle stability control in the presence of human driver. The interaction is defined by forming a differential linear quadratic game between the driver who is controlling the steering angle and the controller which is controlling the brake torques. Evaluated by a nonlinear vehicle model, numerical simulations are presented for a vehicle in the standard fishhook test. Preliminary results show the effectiveness of this controller over a commonly used linear quadratic controller.