Design education has moved towards a collaborative practice where designers work in teams and with other disciplines to solve unstructured problems. Along with the cognitive skills involved in the execution of the design process, designers also need skills to work in teams, share information, negotiate common ground and reach consensus. Conversation is core to establishing successful collaborations and learning for students. In order to assess and facilitate collaboration skills, it will become necessary to understand what constitutes constructive and effective dialogue amongst students. The aim of this research is to compare expert versus novice interdisciplinary teams to understand how to better support teams to engage in constructive dialogue during educational design projects. Two cases were studied across different design domains during the problem definition, ideation and concept development phases of the design process. The cases involved a bio-medical fellowship project and an undergraduate product design project. The teams' conversations were recorded and qualitative content analysis was applied to reveal the cognitive processing and conversation activity that enabled the teams to progress during team collaborations. The findings show that during team interactions design teams alternate between four main cognitive processes, supported by a further six conversation activities to execute the design task. Experts were found to use these cognitive processes and conversation activities more effectively than novices. Recommendations are proposed that can guide design educators to support students during team interactions when solving design problems. The findings have implications for how team work is facilitated and assessed in education.