This paper examines EFL learners' dialogic interaction in the implementation of a computer-mediated communication (CMC) task. Within the framework of sociocultural theory, the research focuses on how learners working in pairs collaboratively perform task management and build relationship in the synchronous CMC context. Sixteen Chinese tertiary EFL learners in eight self-selected pairs worked on an assigned task in the online chat rooms. We had a descriptive analysis of the data obtained from online chat logs, focusing on the task-related talk and off-task talk. Results indicate that learners' task-related talk has a variety of functions and facilitates the establishment and maintenance of task intersubjectivity. The findings also reveal the positive role of off-task talk in facilitating this online learning activity.