Classical action research within single organizations has become a well established and differentiated approach since its inception more than six decades ago. Although new larger scale varieties of action research are beginning to develop, there is still a clear need to expand the scope of action research practice (Greenwood, 2002). Building on previous work, this paper develops multi-site action research (MAR) as a conceptually distinct variant of action research implementation with promising potential to fill the gap between the classical and coalition type varieties of action research. MAR is defined as involving the concurrent implementation of multiple distinct single-site action research processes, with a similar focus, and some level of coordination across sites. From a review of three relevant multi-site initiatives, a conceptual framework for the potential benefits of MAR is derived, and a model of the MAR implementation process is presented and discussed.