In this paper, we solve the output feedback semi-global tracking problem of the nonlinear benchmark RTAC system, in which the reference signals are output trajectories of a simple control systems subject to some input. The introduction of the input enlarges the class of the reference signals that can be tracked. And the proposed solution covers the previous results of output feedback global tracking, namely the solution is still global when the input is zero. Finally, a simulation illustrates the effectiveness of our approach.