Enabling teachers to talk about their professional practice is an essential element of professional development, however the types of conversations required for transformative outcomes are not clearly defined. Teachers from eight Australian primary schools (grade1-7) participated in a collaboratively designed ICT professional development program over a period of 12 months. Teachers conversed through an online threaded discussion forum as well as within small and large group face-to-face meetings as part of their ICT professional development activities. The findings suggest evidence of two types of talk that have a concomitant relationship in the development of transformative practice within ICT professional development: collegial and critical discussion. Collegial discussion is found to be important in developing community and common understandings while critical discussion is vital for its role in transforming teachers' beliefs. The environment in which conversations take place plays a major role in the type of talk in which teachers will engage. The findings of this research inform both ICT professional development for practicing teachers and the functioning and productivity of professional learning in online learning communities.