We report the development of preservice teachers' oral presentation performance based on a technology-mediated video reflection system. Participants video-recorded oral presentations and uploaded them to an online blog to view and reflect on their performance and that of their peers. Four presentations by forty-one participants were analysed using a range of criteria based on what we call the Modes of Communication (voice, body-language, words and alignment between them) and the Constructed Impression of the communication acts (confidence, clarity, engagement and appropriateness). Results indicate a significant improvement across all criteria with a decreased rate of improvement for later iterations.