The topic of power has not featured strongly in debates about organizational learning, a point that is illustrated in a discussion of influential studies of teamworking. Despite the insights that such studies have provided into the nature of expertise and collaboration they have tended not to explore the relevance of issues of hierarchy, politics and institutionalized power relations. The paper addresses the problem by exploring the links between power, expertise and organizational learning. Power is analysed both as the medium for, and the product of, collective activity. The approach emphasizes how skills and imaginations are intertwined with social, technical and institutional structures. While studies of teamworking have concentrated on situations where imaginations and structures are tightly linked, unexpected developments may occur when these relations are loosened. Such situations occur when the needs of the moment overshadow normal routines and relationships and there is no single overview or centre of control. It is suggested that organizational learning can be conceptualized as the movement between familiar and emergent activities and between established and emergent social relations. Events in a two-year action research project are used to illustrate the approach and explore episodes of decentred collaboration.