A full-scale Sequencing Batch Reactor designed for 200 P.E. has been operated with nutrient removal. In aerated periods of the operational cycle the Oxygen Utilization Rate has been calculated on-line based on a standard oxygen probe which is also used for the control of the oxygen supply. It is described how a simple OUR process control strategy can be applied in order to obtain energy savings and optimization of the plant capacity. OUR has been found to be very valuable for on-line and off-line process control at small nutrient removing waste water treatment plants. A true batch system as the SBR provides the optimum conditions for the installation of OUR process control, but it can also be applied in other alternating activated sludge plants.