This paper describes the construction and testing of a model designed to inform contributors to online collaborative dialogues about the nature of their contribution, and to guide the input from tutors who facilitate these dialogues. In particular, the model was designed to assist reflection on learning behaviours in online dialogues by participants and by tutors. The overall goal was to generate a model to help groups construct knowledge through reflection on their own contributions--rather than to provide a means for external evaluation of individual progress. To develop the model, a participatory action research methodology was used, involving interested parties in a spiral of exploration, planning, implementation, systematic observation, reflection and then re-planning. After clarification of the objective of the action research, a range of learning theories were reviewed; then constructs used in the evaluation of online learning were considered. From this reconnaissance, a prototype model was constructed. This was used by three groups actively involved in online collaboration. A synthesis of their evaluative feedback was made on the basis of which a further model was designed and then evaluated. This resulted in the authors' current model, which is presented and then itself tested. (Contains 3 tables and 2 figures.)