There has been an evolution in the teacher professional learning literature on what constitutes effective process. This evolution has seen a shift from a focus on the design elements to the theory of action that integrates and drives these disparate elements to create effective professional learning. This study argues that a focus on a theory of action can be enhanced when the construct of teacher collective efficacy is considered in relation to teacher professional learning. This study examined how participation in a collaborative professional learning model for primary science impacted on the teachers' sense of their collective efficacy in a specific context in Australia. Data from interviews, professional learning sessions, written reflections and classroom observations of a group of 12 primary teachers were analysed using the construct of teacher collective efficacy. The evidence from this case study suggests that teacher collective efficacy employed as a conceptual framework may be a useful design heuristic that might enhance the quality of a teacher's professional learning experience.