There have been more and more Combined Cycle plants being built in recent years due to the efficiency and flexibility they provide. Modeling Combined Cycle plants in the unit commitment problem is very challenging. Combined Cycle units can be operated in various operational modes; however, implementing detailed physical components of a Combined Cycle Plant in market operation is not practical due to model complexity and absence of data. This paper discusses the use of configuration based Combined Cycle model in MISO unit commitment. The usage of a transition cost matrix is proposed to represent additional expenses incurred due to starting up extra units when switching from one operating mode to another. This model represents an approach to overcome the dilemma of preserving accuracy and maintaining practicability while ensuring a more economic solution.