Discussion forums play a central role in online course activities and for the development of a community of inquiry. As part of a larger multi-case study investigating the negotiation of teaching presence in international online contexts, we were specifically interested in how instructors conceptualized their online teaching context, and how they directed their teaching presence in relation to this conceptualization. Conceptualization refers to how an instructor viewed the purpose and goals of the discussion forums. Using Cultural Historical Activity Theory (Engestrom, 1999, 2001) as a framework for analysis, we demonstrate that there is considerable variation in how instructors conceptualized the discussion forum, even in cases of co-instruction where instructors were participating in the same forums. We will discuss how teaching presence was influenced by their conceptualizations and how teaching presence was affected when their conceptualizations conflicted with the course design. We will highlight the implications for instructional design and for teaching in international contexts.