The Effective Classroom Interactions (ECI) online courses were designed to provide an engaging, effective and scalable approach to enhancing early childhood teachers' use of classroom practices that impact children's school readiness. The created courses included several versions aimed at testing whether or not certain design aspects could increase participation and subsequent learning outcomes. The purpose of this study was to examine the extent to which early childhood teachers accessed the courses and varied in their (a) participation in the core course content and (b) optional discussion board as a result of the course experience they were assigned to as well as individual characteristics that may be associated with participation. As might be expected, findings indicated that early childhood teachers accessed the course often on nights and weekends, even though participating centers allowed their teachers to do coursework during work time. In addition, participants reported high levels of satisfaction with their experience. Both persistence in the ECI courses and overall completion of activities were higher than those reported in other studies of online learning. The participation of early childhood educator teachers was consistently predicted by comfort with technology, credit or non-credit status and assignment to the group that included regular conferences with the instructor. These relationships, however, did not always occur in expected ways. Implications for exploring online learning as a feasible option for early childhood educators are discussed. (author abstract)