The variationist perspective provides tools for modeling language use in context by incorporating the influences of social and linguistic factors in the interactional setting. These influencing factors include speaker characteristics (age, regional origin), characteristics of the setting (formality), and characteristics of other participants in the interaction (Geeslin & Long, 2014). In second language research, these factors can describe change over time (i.e., development) and the acquisition of sociolinguistic competence (i.e., the ability to modify one’s speech in socially acceptable ways across settings) (Canale & Swain, 1980; Tarone, 2007). While the variationist perspective is well equipped for addressing the role of the interlocutor, the potential of variationist tools has not been fully exploited. The present chapter reviews existing variationist research, provides a new model that includes these interlocutor-related factors, and proposes a research agenda for moving forward.