This qualitative study followed the work of 12 principals and their supervisors to understand the concept of joint work as consequential for principals' learning and practice development. Research questions centered on the principal supervisor and principal's key work tasks and the situational contexts in which they occurred. Findings revealed that key joint work tasks included development of tools; classroom observations; and planning, facilitating, and reflecting on leading teams. These tasks occurred both in a dyad and in the context of school-based teams. Joint work in teams led to greater opportunities for principals' and other school based leaders' instructional leadership learning.