This study explored preservice elementary teachers' and their mentors' understanding of the essential features of inquiry-based teaching through the use of evidence-based reflection. The web-based video analysis tool (VAT) system was used to support preservice teachers' and mentors' evidence-based reflection during field experiences. Major data sources included VAT reflections and individual interviews. Data analysis indicated that the preservice teachers had been involved in various activities designed to support their understanding of inquiry features in a science methods class; they did not implement all of the features in their actual teaching. Both preservice teachers and mentors had difficulty connecting appropriate inquiry features to each teaching episode, which indicates their lack of understanding of inquiry. Both the preservice teachers and mentors had different levels of understanding for each feature. That is, they tended to understand certain features better than others. They interpreted each feature of inquiry-based science teaching too broadly. They also either had a teacher-centered view or tended to focus on issues unrelated to science teaching.