In this report of an action research study, the authors describe how one elementary science teacher educator used transcript coding of simulated classroom discussions as a pedagogical approach to learn about her elementary preservice teachers' (PSTs') abilities to notice key aspects of scientific argumentation discussions. Elementary PSTs (n = 19) enrolled in a science methods course engaged in transcript coding before and after facilitating their own argumentation discussions in the Mursion® simulated classroom environment with five upper-elementary student avatars. The first transcript was from a PST outside of the course; the second was from PSTs' own discussions. The study examined how PSTs' coding of the transcripts could provide the teacher educator with insights regarding PSTs' noticing about engaging students in argument construction and critique. The study also aimed to investigate PSTs' perspectives on the utility of transcript coding. Findings showed that PSTs can code with accuracy, yet they may be more apt to miss coding teacher prompts that encourage students to share reasoning. Results also revealed that PSTs sometimes coded nonexamples of argument construction and critique, suggesting a need for more targeted learning experiences to connect teaching principles with classroom interactions, and the PSTs perceived coding their own and other's transcripts as uniquely valuable learning experiences.