Increasingly, teacher involvement in collaborative design of curriculum is viewed as a form of professional development. However, the research base for this stance is limited. While it is assumed that the activities teachers undertake during collaborative design of curricular materials can be beneficial for teacher learning, only a few studies involving such efforts exist. Additionally many lack specific theoretical frameworks for robust investigation of teacher learning by design. The situative perspective articulated by Greeno et al. (1998) and third-generation activity theory as developed by Engeström (1987) constitute useful conceptual frameworks to describe and investigate teacher learning by collaborative design. In this contribution, three key features derived from these two theories, "situatedness," "agency" and the "cyclical nature of learning and change," are used to describe three cases of collaborative design in three different settings. Grounded on this theoretical basis and a synthesis of the three case descriptions, we propose an empirically and theoretically informed agenda for studying teacher learning by collaborative design.