Over the years, research on writing has increasingly emphasized the value of adopting a sociocultural perspective to understand how social context and social interaction relate to writing regulation. Using the theoretical lens of participatory appropriation, this study investigates the self regulatory behavior of three successful Bachelor essay writers in literature, and how the interaction with their supervisors supported students' development of writing regulation in disciplinary relevant ways. Data was collected through in-depth qualitative interviews at three key moments in the term; Pintrich's self-regulation framework was used as coding heuristic to trace participants' self-regulation behavior over the term. Self-regulation data was cross-analyzed with data coded as participatory appropriation to identify the overlap between students' self-regulation of writing and their social experiences, especially the dialogue with their supervisors. Our results show how the supervisors acted as agents of socialization, providing frames for adoption of disciplinary-relevant ways of thinking and doing, as well as indirectly sustaining the students' motivation and re conceptualization of the writing experience. Overall, this investigation responds to calls for inquiries of self-regulation against the backdrop of the social context in which it is embedded.