A simple technique of designing a robust model reference discrete-time variable structure output tracking controller for a class of perturbed MIMO linear systems is proposed in this paper. Both an adaptive mechanism and a perturbation estimation process are embedded in the proposed control scheme so that the upper bound of the perturbation estimation error is not required. It is shown that the tracking error will be constrained in a small bounded region, and the stability of the overall controlled system is guaranteed. A numerical example is given to demonstrate the feasibility of the proposed control scheme.