This chapter demonstrates how problem-based peer group mentoring in groups can facilitate change and learning in an organisation. This is exemplified by a five-year project at a humanities faculty at a large, research-based university, where the supervisors of master's students discussed their supervision-related problems in groups following a strictly structured method, termed as problem-based peer group mentoring (PPGM). Throughout the course, it became evident that the problems were related to the role of supervision not only at an individual (micro) level but, to a large extent, at an organisational (macro) level. The goal of the project was to encourage a culture of collaboration among the teachers. This goal seemed to be fulfilled during the semester of the PPGM course, though few long-term changes in supervision practices were evident. However, we found that interesting changes took place at an organisational level, although this was not the initial goal of the project. We argue that in addition to the peer group mentoring model, bringing participants together from different departments encouraged knowledge-sharing across the institution and contributed to organisational learning. To know if lasting organisational learning takes place, we suggest that structural components must be taken into consideration in the design of PPGM initiatives and that measures are taken to document and evaluate change-for example, in routines and practices. Previous research on organisational learning supports this conclusion (Argote 2012