Organizations deploy advanced communication media such as audio and videoconferencing to enhance and extend group communication interactions. However, established groups (i.e., groups with a history of working together) can view and use the same technology differently from groups without any past experiences of working together. This study examines the relative influences of media condition and group cohesion on social presence, task participation, and group consensus. Results from a controlled laboratory experiment with 45 triads of college students working on a decision-making task showed that media condition (audio conferencing vs. desktop videoconferencing) has significantly smaller influences on social presence and task participation than group cohesion in established groups. The study found that influence of group cohesion over social presence is additive, rather than substitutive, to that of media condition. The study also established that task participation played a more important role than social presence in determining the degree of consensus among group members in computer-mediated communication environments.