This is a study in the field of EFL teacher learning (how to teach process writing) - with an emphasis on the development of teachers' understanding of their subject matter (the academic tradition) - through an eclectic, reflective, inquiry-oriented and collaborative teacher education strategy - 'Collaborative Reflection and Inquiry'. The study aimed at inquiring into the relationship between the supervisory approach and the professional development of teachers as well as into the way it might promote that growth. Results suggest that the teachers involved in the study changed their knowledge, skills and dispositions and that these changes were due to the integrated approach to supervision. There is also some evidence that the teachers' content knowledge, beliefs and dispositions affected the impact of the supervisory strategy. In this paper, we deal particularly with this last result of the study and consider some implications of it for pre-service teacher education.