While Writing Studies scholars have embraced research on multilingualism, writing scholars have not developed program assessment methods that are informed by that scholarship. This profile describes a program assessment design that was informed by research on multilingualism, super-diversity, and consequential validity. This design included student survey data, student interviews, scoring data, and institutional data with specific attention to language and mobility. Such a design allowed us to capture multiple sources of evidence to make valid inferences about the writing of a complex population. Moreover, the bottom-up collaborative process used in this assessment design echoed the program’s deep-rooted commitment to social justice in ongoing program research.