We develop a theory of institutional field change with project organizing at its heart by posing the question of how projects contribute to institutional field change. We do this by bringing together recent literature on institutional projects with that on institutional logics and institutional complexity to show how institutional projects can act as vectors of change in institutional fields by offering bounded spaces for working through the implications of institutional complexity. We then explore this contention empirically by examining the implementation of strategic field change in a mature, complex, institutional field. We contribute to theory in project organizing research in four ways. First, we show how projects can be complements to hybrid organizations in fields displaying volatile complexity to achieve institutional field change. Second, we respond to the call to link institutional projects with institutional logics and thereby place project organizing at the heart of change in complex institutional fields; third, we demonstrate how change in the institutional field both shapes and is shaped by interactions across the commercial interface between project owner organizations and project-based firms. Fourth we show how the development of institutional theory in project organizing research depends upon a full theorization of the institutional field in which the project is embedded.