Teacher preparation is an integral factor in education. The purpose of this qualitative descriptive study was to explore how pre-service teachers enrolled in teaching methods courses at two private Christian universities in the Southwestern United States described content knowledge using reflection-on-action after the planning, teaching, and feedback stages of microteaching. This research emerged from a clear gap that existed on this topic in prior and current literature. This study was theoretically supported by Schön’s reflective practitioner model, specifically reflection-on-action, which occurs retrospectively, shortly after an event such as teaching has occurred. Three research questions explored how pre-service teachers describe content knowledge using reflection-on-action after the planning, teaching, and feedback stages of microteaching. Purposive sampling was used to recruit 11 pre-service teachers who had participated in microteaching sessions in their university or practicum classrooms. Data were collected using semi-structured conversational interviews and a questionnaire. Through thematic analysis, eight themes were identified: rely on prior knowledge, benefit from collaboration, compensate when faced with unfamiliar content, planning stage strengthens content knowledge, confident due to background knowledge, teaching stage strengthens content knowledge, validated content knowledge, and feedback stage strengthens content knowledge. Findings of the study suggest that pre-service teachers benefit from engaging in reflection-on-action as a tool to facilitate growth and development of content knowledge specific to their degree program and future teacher employment.