This paper focuses on the use of multimedia-based predict--observe--explain (POE) tasks to facilitate small group learning conversations. Although the tasks were given to pairs of students as a diagnostic tool to elicit their pre-instructional physics conceptions, they also provided a peer learning opportunity for students. The study adopted a social constructivist perspective to analyse and interpret the student's conversations, focussing on students' articulation and justification of their own science conceptions, clarification of and critical reflection on their partners' views, and negotiation of new, shared meanings. Two senior science classes participated in this interpretive study. Data sources were mainly qualitative and included audio and video recordings of students' small group discussions at the computer, interviews with selected students and their teachers, classroom observations, and student surveys. Findings indicate that the computer-based POE tasks supported students' peer learning conversations, particularly during the prediction, reasoning and observation stages of the POE strategy. The increased level of student control of the POE tasks, combined with the multimedia nature of the program, initiated quality peer discussions. The findings have implications for authentic, technology-mediated learning in science.