Developing collective professional capacity in schools is viewed as important for improving schools. Furthermore, principals are seen as being in a key position to promote the development of collective capacity. Although an array of studies report on what principals can do to support capacity development, such as by facilitating collective professional discussions among their staff, less attention has been drawn to how principals can engage in and lead such discussions. In this article, we present and use a conceptual model for leading professional group discussions to examine leadership of professional group discussions performed by principals in a Norwegian National School Leadership Program. The findings show that the principals' focus is on fostering an open process by involving all participants in a way that gives all members a chance to provide their opinions and to have their thoughts heard. The principals pay less attention to the types of actions considered essential to keep discussions on track and carry them forward, including making further plans for actions. Because group discussions can lay the groundwork for building professional capacity and real improvement in schools, more awareness is needed for principals so that they can develop the skills needed for leading professional discussions.