A system for controlling steam temperature in a boiler uses a time delay feedback controller known as a Smith Predictor to provide control tuning of true boiler parameters which change with load. More specifically, a feedforward predictor (38) presets an expected secondary superheater inlet temperature with a boiler load, the expected temperature is corrected for firing rate deviation, air flow deviation and reheat temperature control by respective modifiers (42, 44 and 46), a final correction is effected by a feedback controller (50), and a cascade controller (48) responds to the inlet temperature to provide rapid process loop response to predictable intermediate process control points.