Dialogue is central to the collaborative processes of inquiry-based approaches. In this methodological article on Interactional Ethnography (IE), we outline the guiding principles of IE as a logic of inquiry for studying the talk and actions of learners and their mentors in inquiry-based learning. Through a telling case of facilitation processes in high school invention education (IvE), we illustrate the major steps and analytic processes that an IE research team undertakes to collect, archive, and analyze records of classroom learning. We share how the IE team enters this ethnographic space and undertakes video-enabled microethnographic discourse analyses of in-time and over time events to identify key learning processes and develop warranted interpretations. Specifically, we exemplify how the ethnographers conduct nuanced analyses of learning discourse in-the-moment and over time. In the context of invention education, we share how an IE study enables the researchers to trace the developing cycle of inquiry and make visible the processes that support design thinking in invention education.