Cohesiveness in teams is an essential part of ensuring the smooth running of task-oriented groups. Research in social psychology and management has shown that good cohesion in groups can be correlated with team effectiveness or productivity, so automatically estimating group cohesion for team training can be a useful tool. This paper addresses the problem of analyzing group behavior within the context of cohesion. Four hours of audio-visual group meeting data were used for collecting annotations on the cohesiveness of four-participant teams. We propose a series of audio and video features, which are inspired by findings in the social sciences literature. Our study is validated on a set of 61 2-min meeting segments which showed high agreement amongst human annotators when asked to identify meetings that have high or low cohesion.