This research reports data from case studies of three intermediary organizations facing the challenge of scaling up teacher learning. The turn of the century launched scaling up efforts of all three intermediaries, growing from intimate groups, where founding teachers and staff were key supports for teacher learning, to large multi-state organizations. The authors drew on data from three earlier qualitative studies of professional development at Big Picture Learning, Expeditionary Learning, and the Internationals Network, and reveal some of the benefits and challenges of taking teacher learning to scale.