In the paper a method is proposed to design a periodic output feedback controller for a singularly perturbed discrete system. A state feedback controller designed from the singularly perturbed discrete system has been used to compute output injection gain. This output injection gain has been used to compute the periodic output feedback gain. The method does not require the states of the system for feedback. The method is illustrated by a practical example of a fifth order steam power system. © IEE, 1999.