This classroom-based research aims to investigate the nature and quality of talk in synchronous computer-mediated communication (SCMC) among Vietnamese tertiary EFL learners. Participants included 60 students in their sixth semester of an eight-semester BA in TESOL program in a large university in Central Vietnam. Using a sociocultural lens, the nature of discussion was compared in two modes of exchanges, SCMC versus face-to-face (FTF), through analysis of discussion transcripts supported by questionnaire data, interviews and observations. The first level of analysis, participation, revealed that the online students, collaborating in an academic task for the first time via SCMC, produced fewer words, but spent more time, during the discussion process. More equal contribution was a marked feature of the SCMC mode. For the second level of analysis examining the interactional nature and pattern of discussion, transcripts were analyzed according to socioaffective, organizational and sociocognitive themes, and their emergent subcategories. Clear differences were evident between the two settings regarding group processes, leadership, negotiation and consensus. It is argued that for these tertiary Vietnamese EFL learners, the FTF groups were more product-oriented in the discussion task, while the online groups presented a more process-oriented style of learning.