This work in progress reports preliminary findings from a study of six teams in a well-established Problem Based Learning (PBL) curriculum. As PBL gains popularity in engineering curricula, it is increasingly important to understand faculty roles in order to best prepare faculty for this type of teaching and to effectively design meaningful learning environments. Because PBL facilitation requires skills and techniques that differ markedly from traditional content-delivery modes, engineering faculty need a clear model to describe their roles and practices in such an environment. To develop such a model, we employ the theory of cognitive apprenticeship to analyze audio-video recorded sessions of PBL in engineering.