Writing groups have been gaining attention as a new approach to doctoral education to cater to students and supervisors' diversified needs emerging from the globalisation of higher education. However, the relationships between the main activity of these groups, oral interactions, and participants' learning remain unexplored. To fill this gap, this study investigates the processes of one multilingual PhD student's genre learning through oral interaction in a 10-week writing group at an Australian university. Data were collected through observation and audio recordings of meetings, written drafts, and interviews with the student and a facilitator. As mediating artefacts, writing group oral interactions were closely examined with reference to the student's motives and her subsequent writing. Specifically they were analysed for the means of scaffolding and the student's response patterns. The findings suggest the influence of the student's motives on her participation in the activity of the writing group as well as her decisions on how to deal with the scaffolding she received. The findings reveal dynamic relationships between motives, scaffolding, and the Zone of Proximal Development (ZPD), and shed new light on the facilitative role of learners' responses to scaffolding. The article concludes with pedagogical implications for oral feedback sessions in classrooms and writing groups.