This thematic analysis utilizes teacher insights from their experiences in an online professional development (PD) course on early reading instruction to determine course design features educators perceive as being beneficial and questions and concerns educators raised during the course. We analyzed discussion forum contributions and course surveys from 418 educators enrolled in the course. We found that videos, interactive activities, and discussion forums were features of the online platform that fostered critical teacher reflection. Also, as teachers engaged with literacy content, they sought out new ways of understanding concepts of word analysis and invented spelling and reflected on how their course learning might apply to meeting the needs of diverse learners. Implications and design recommendations for future professional development courses in foundational reading are discussed.