In large software development projects, coordination is considered critical for the success of system development. Generally, coordination focuses on managing interdependencies among different organizational units within one organization. However, in IS outsourcing the interdependencies reach beyond organizational boundaries into coordination of development between a software vendor and a client company. Our research focuses on coordination of development in a setting where several vendors and client organizations develop a common information system. In this study we investigate the characteristic features of system development in a multiple customer environment. Especially we look at the coordination mechanisms and their evolution over time and phases of system development. Our analysis shows that the coordination mechanisms become more formal and control-oriented as the jointly developed system becomes more and more functional. Subsequently changes to the system become harder to get through the coordination mechanisms.