This paper explores teachers’ and teacher assistants’ self-efficacy of delivering PrepSTART, a classroom based, oral language and early literacy program for five-year-old students. In the current study, speech pathologists developed, provided training and monitored program implementation. Teachers and teacher assistants (n = 17) shared their experiences of delivering PrepSTART through a series of focus groups. A content analysis was conducted to determine key themes in participant responses. These themes were then analysed in relation to the four self-efficacy components (mastery, experience, vicarious experience, verbal persuasion and emotional arousal). Differences in levels of understanding about oral language development, communication between professionals, and the importance of building networks emerged as key themes. An improved understanding of the self-efficacy of professionals regarding the implementation of oral language programs will further facilitate the interdisciplinary approach that is needed to promote early academic success for students.