In 2020, the state of Florida strategized to improve reading instruction for K-12 students by mandating all elementary and literacy teachers receive a reading endorsement. In response to the mandate, the University of Florida's Lastinger Center for Learning developed an online, asynchronous, self-paced teacher professional development program to serve large numbers of teachers. By design, the self-paced program does not include collaboration among learners but does rely on a facilitator to guide learners toward successful completion. While there is some literature on the roles of online facilitators in online learning environments (e.g. Berge, 1995; Martin et al. 2018), I wanted to understand the role of the facilitator within the unique design of this scaled up, self-paced online professional development. For this qualitative case study, I sought to answer the research question: What supports does an excellent facilitator provide in an online professional development program that contribute to participant completion? Data sources included three semi-structured elicitation interviews, observations, and documents from one course facilitator, resulting in close to 250 pages of data. Several themes emerged from the analysis of my data. I found that Myrtle, the facilitator, used many of the facilitation techniques found in the online facilitation frameworks (Berge, 1995; Martin et al., 2018) such as pedagogical, social, managerial, and technical support. However, she used additional strategies that were less visible to her learners because they occurred behind the scenes to organize and document learner progress. In addition to these facilitation strategies, Myrtle addressed the diverse linguistic needs of her learners whose first language was not English. My findings provide suggestions for how to support high quality professional development within an online, asynchronous self-paced learning environment. This study adds to our understanding of the role of online facilitators, both broadly and more locally within the context of the Literacy Matrix, as it expands to meet the growing needs of the Florida teaching workforce. Improving online professional learning for literacy teachers can contribute to improved student outcomes in reading. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]