ABSTRACT Text-based discussion is a form of disciplinary literacy that engages students in collaboratively building understanding of texts. It is a form of instruction that benefits students’ reading comprehension, but is rarely used in classrooms, despite its potential. This rarity may be because facilitating discussion requires teachers to have specialized knowledge of text. Specifically, teachers must understand how authors use discipline-specific text features and language patterns to convey meaning and how readers notice and evaluate these aspects of texts as they build textual understandings. This mixed methods study adopts a convergent-parallel design to investigate the effects of a 14-week intervention on pre-service teachers’ (PSTs) acquisition of specialized knowledge and its application to text-based discussions conducted with students in field placements. Findings suggest that the intervention improved PSTs’ specialized knowledge and that teachers felt more prepared for their discussions after applying their knowledge when planning discussions. However, even at the end of the intervention, PSTs continued to demonstrate gaps in their specialized knowledge, which influenced their ability to lead text-based discussions. The findings have implications for teacher educators attempting to prepare novice teachers for text-based discussions.