Various forms of mentoring and 'collegial learning' are often used to enhance teachers' continued professional development. When teachers come together to scrutinise their own questions raised from practice, sustainable changes in teaching and classroom situations increase. To understand what happens in the practice of continuing professional development (CPD), and to examine what professional learning is possible in the specific practice, it is crucial to examine the arrangements that hold the practice in place. In this chapter, a practice of teachers'professional group mentoring is examined through the lens of practice architectures. Foucault's notion of power is also used as a theoretical frame. This analytical approach brings new insight to what enables and constrains professional learning in mentoring practices.