This design-based research aims to improve the quality of graduate supervision using a Massive Open Online Course (MOOC). The Quality Graduate Supervision MOOC brings interdisciplinary faculty, postdoctoral scholars, and expert supervisors together in an online learning community to discuss and consider effective supervision practice, strategies for relationship building, supports for academic writing, mentoring for diverse careers, and how to combine excellence and wellness. The survey, interview, and system data were analyzed to inform and assess the design and development of the QGS MOOC, to gain insights into learner experience and engagement, and to assess the impact of the online learning community on graduate supervision practices. Through ongoing design and evaluation of this online learning course for graduate supervisors, the research team found the learning community influenced faculty members' awareness, collective knowledge building, goal setting, and actions for graduate supervision practice. We present results from our evaluation of the design components in the QGS MOOC, the learning benefits for supervisors, impacts on graduate supervision practice, and make several recommendations for research and practice.