This paper examines learning in interdisciplinary action teams.Research on team effectiveness has focused primarily on single-discipline teams engaged in routine production tasks and,less often,on interdisciplinary teams engaged in discussion and management rather than action. The resulting models do not explain differences in learning in interdisciplinary action teams. Members of these teams must coordinate action in uncertain,fast-paced situations,and the extent to which they are comfortable speaking up with observations, questions, and concerns may critically influence team outcomes. To explore what leaders of action teams do to promote speaking up and other proactive coordination behaviours – as well as how organizational context may affect these team processes and outcomes – I analysed qualitative and quantitative data from 16 operating room teams learning to use a new technology for cardiac surgery. Team leader coaching, ease of speaking up, and boundary spanning were associated with successful technology implementation. The most effective leaders helped teams learn by communicating a motivating rationale for change and by minimizing concerns about power and status differences to promote speaking up in the service of learning.