This chapter reports on a collaborative dialogue (Scarino, 2016) between a language assessment researcher and an expert language teacher with the aim of exploring how theory and practice might inform each other. Following the Hill (2017) framework, the study started with the following questions: What does the teacher do?What does she look for? What theories, understandings or beliefs inform her feedback practices? What are learners’ understandings of feedback? How does the teaching context influence the nature and content of feedback? Participants comprised 15 students from beginner (CEFR A1), intermediate (CEFR B1), and advanced (CEFR C) levels of a university-level Spanish program. Data comprised copies of written feedback, recordings and transcription of unstructured think-aloud protocols , and semi-structured interviews, and reflective journals . Data were analysed using thematic content analysis. Discussion will focused on the ways in which the collaboration served to advance both theory and practice as well as highlight issues warranting further research.