Proper selection of control parameters is critically important since it has a large impact on the end product and enables keeping the operation run within the specified limits. It also helps to maximize profitability, to ensure quality and safety. In this paper, we will develop a Robust Gain-Scheduled (RGS) methodology that combines between the uses of: robust design to determine the optimal value of process parameters so that the controller maintains the process on target with low variability while keeping the performance robust against the external factors, and gain scheduling to modify the control parameters depending on the state of the system to maintain its stability. An example for carbonated beverage filling process is also presented.