Efforts by universities in sub-Sahara Africa to promote professional development of instructors in course design and delivery by e-learning technologies have often lacked meaningful impacts. This study investigated the impact of collaborative course design on instructors' professional learning about design and delivery of e-learning courses at the Open University of Tanzania (OUT). SixTeacher Design Teams (TDTs), each with 2 instructors, participated in the study, redesigning their print-based courses using an offline Moodle LMS supported by emails and mobile phones. A total of 36 interviews were conducted with 12 instructors, after each of the two workshops and after the course redesign process. Results showed that despite challenges, instructors were satisfied with collaborative course design and they reported that the strategy contributed to their professional learning. Instructors' backgrounds determined the kinds of support needed during course design and delivery.