This paper describes research undertaken for the design of an Online Learning (OL) Module using a Problem-based Learning (PBL) approach in an in-service teacher training course, namely, a Postgraduate Diploma in Third Level Learning and Teaching. This qualification is offered to lecturers from a range of higher education institutions in the Republic of Ireland. Therefore, the "students" who enter upon this module are Faculty or academic staff currently lecturing in Higher Education who are taking this module part-time. They are hitherto referred to as participants. This module is one of eight offered on the Postgraduate Diploma. Attendance for the module is for three hours per week for a duration of ten weeks. Online participation is negotiated with the participants in their PBL group. This PG Diploma is entirely voluntary and only lecturers who are keen to implement novel pedagogical approaches in their own subject disciplines apply for a place on the modules. The aim of the OL/PBL module is to enable the participants to become aware of the practicalities of developing, delivering, supporting and evaluating an online course in their own subject discipline; but the key to their success is by using the principles of PBL to share valuable information with their colleagues from a variety of other disciplines. (Contains 1 figure.)