We present analyses of teacher professional growth during collaboration between science teachers and science education researchers, with special focus on how the differential assumption of responsibility between teachers and researchers affected the growth processes. The collaboration centered on a new conceptual framework introduced by the researchers, which aimed at empowering teachers to plan teaching in accordance with perceived purposes. Seven joint planning meetings between teachers and researchers were analyzed, both quantitatively concerning the extent to which the introduced framework became part of the discussions and qualitatively through the interconnected model of teacher professional growth. The collaboration went through three distinct phases characterized by how and the extent to which the teachers made use of the new framework. The change sequences identified in relation to each phase show that teacher recognition of salient outcomes from the framework was important for professional growth to occur. Moreover, our data suggest that this recognition may have been facilitated because the researchers, in initial phases of the collaboration, took increased responsibility for the implementation of the new framework. We conclude that although this differential assumption of responsibility may result in unequal distribution of power between teachers and researchers, it may at the same time mean more equal distribution of concrete work required as well as the inevitable risks associated with pedagogical innovation and introduction of research-based knowledge into science teachers' practice.