Although writing plays a significant role in communication, 21st century literacies and academic foreign language learning, little research has investigated approaches to and instructional practices of writing in foreign language (FL) contexts. To address this gap, the current study explores how postsecondary FL teachers conceptualize writing instruction and apply their conceptual knowledge in the classroom. Using a sociocultural theory perspective, this qualitative study focuses on genre-based writing instruction and the teaching of textual borrowing among three graduate teaching assistants in a lower-level French as a FL course. Findings, based on analysis of classroom observations, teaching materials, and interviews, demonstrate that participants’ conceptualizations and implementation of textual borrowing were emergent, variable, and influenced by their everyday understandings and experiences of writing. These findings suggest several implications for FL writing instruction and teacher professional development and lay the groundwork for future investigations into how writing pedagogy is implemented in postsecondary FL programs.