This paper explores how teachers in a K-12 foreign language (FL) department experienced a school-wide, sustained professional development program designed to integrate multicultural curriculum across all disciplines using James Banks' (2005) framework while simultaneously revamping assessment practices through Wiggins and McTighe's (1999) backward design for classroom assessment. Data reveal that the initiative challenged and affirmed teachers in terms of what is "multicultural" in a FL curriculum. While sustained and embedded professional development is touted as best practice in professional development, some teachers in this study experienced weariness from the process, which was sometimes perceived as having an unclear vision. Data also suggest some important differences in how the professional development initiative was perceived by U.S.-born, native English speakers and non-U.S.-born, nonnative English speakers. Challenges of and recommendations for meeting the disciplinary and individual teacher's needs within a school-wide curriculum transformation initiative are discussed.