Massive Open Online Courses (MOOCs) have experienced rapid growth and attracted significant attention within academia. However, despite widespread acceptance of MOOCs as a unique opportunity to transform educational practices, many questions remain regarding their sustainability, given the high dropout rates and challenges related to collaborative learning support . Recent research has attempted to address these concerns by analyzing students' MOOC experiences and how MOOCs may fall short in meeting students' learning needs . However, very little research has approached the problem from an instructor perspective. We report an interview study of 14 MOOC instructors in which we used grounded theory to uncover the complex processes, motivations, and challenges associated with teaching a MOOC. A key finding is that we should provide support through the whole instruction process. By enhancing support for instructors and their MOOC collaborators, we may improve outcomes for all MOOC stakeholders, including students.