Fostering students' ability to engage in scientific argumentation is an essential component of science teaching.. Unfortunately, research shows that teachers often lack sufficient prior experiences. As teacher educators, we sought to better understand how to effectively provide such critical experiences. Furthermore, we wanted to understand how the engagement in those activities was shaped by the methods instructor's own discourse. The purpose of this study was to shed light on the discursive practices preservice teachers used as they constructed a series of scientific arguments. Specifically, we sought to understand how argumentation discourse evolved as the preservice teachers went through the sequence of activities. The guiding research questions were: 1) What role does institutional talk play in shaping PSTs' discursive construction of scientific arguments? 2) How does PSTs' use of institutional talk evolve over the course of four argumentation activities? We drew upon discursive psychology and conversation analysis to show how twenty-one preservice teachers' talk functioned to build arguments, as well as how their talk evolved over the course of the four targeted activities. The findings illustrate how the preservice teachers revealed the institutionality within their talk by orienting towards classroom norms. The resulting understandings are used to provide recommendation for science teacher educators.