Cultural historical activity theory (CHAT) perspectives are used to shed light on an extended teacher-researcher collaboration, at a Grade 4-6 school in Sweden. Beginning with participant observation and emerging forms of engagement like co-authorship of research reports, the collaboration is understood as expansive learning activity. Treating the practices of teaching and research as distinct yet collaborating activity systems within this, provides an opportunity to analyse the manner in which joint conduct of project related instructional interventions became shared object. This also enabled teacher and researcher to become active stakeholders in each other's practice. Dialectical realisation of stakeholdership and shared object led to reconceptualisation and transformation of the very horizons of our work.