When discussing the performance of design teams, researchers repeatedly stress the key role of team cognition, which refers to collective cognitive structures and processes relating to product conceptualization and realization. The perspective taken in this chapter is that individual team member knowledge contributes to team cognition, and the quality of the aggregation of knowledge explains variance in knowledge-intensive activities such a design. We will describe two methods that together assess the structure and processes of team cognition and their impact on design team performance. Taken together, these methods provide a way to assess team cognition over time so as to account for variance in team performance based upon the quality of their knowledge practices.