This qualitative case study explored the experiences of eight observing teachers, a demonstration teacher, and a program department consultant, who over a nine-month period participated in a demonstration classroom professional development initiative. Analyses of participants' experiences documented how the initiative created a catalyst for changes in observing teachers' beliefs and practices. Factors identified as those supporting their change processes included: the provision of "believable" vicarious experiences in a local school context; the demonstration teacher's exemplary mentoring skills and respect for observing teachers' professional decision-making; the cohesion created by tri-level alignment of programming goals; and the on-going support provided to observing teachers. While this study affirmed that demonstration classrooms hold the potential to promote teacher change, it highlighted the importance of the selection of mentor teachers who are willing and able to provide differentiated professional learning, and the significance of attending to the organizational elements of such opportunities.