Taking a sociocultural theory perspective (Lantolf & Thorne, 2006), this longitudinal study explored the conceptual development of two teaching assistants in a university foreign language department in relation to literacy and language teaching. Findings illustrate the "twisting path" (Vygotsky, 1987, p. 156) of concept development experienced by the two first-time teachers of Spanish as their understandings of literacy and efforts to use tools of literacy evolved over several years. Evidence of the ability to think through concepts of literacy in structuring teaching practices did not emerge for either participant until four semesters after they started teaching, illustrating what a gradual and often difficult process teachers' conceptual development is, requiring multiple, sustained opportunities for dialogic mediating, scaffolded learning, and assisted performance (Johnson, 2009).