A method of operating a furnace having process tubes and multiple burners where it is desired to conform the temperatures of the process tubes to selected target temperature criterion. The present method provides a systematic and quantitative approach to determine how to adjust burner flow rates to result in desired tube wall temperatures, for example, using objective functions to decrease the probability that temperatures pertaining to the plurality of process tubes exceed their selected limit temperatures. An objective function can also be used to reduce the excess oxidant requirement for the furnace.