With a growing recognition of the need to go beyond text and look into the context where the writing (or the teaching/learning of it) takes place, the ethnographic perspective has been fruitfully adopted in academic writing research. The present study, integrating the perspective of genre and ethnography as methodology, probed into the context of L2 English writing instruction in a Chinese university where three writing-related courses were offered to English majors throughout the curriculum. Through a sustained engagement in the courses under focus, we collected multiple types of data, such as the students' writing samples, documents, teaching materials, and semi-structured interviews with students and course instructors, in an attempt to give a rich account of the core participants' real-life experiences in teaching and learning L2 English writing. Results demonstrated that, although informed by the same national syllabus, the L2 writing instruction in reality consisted of a pedagogical "mosaic" that included the traditionalist, process-based and genre-based approaches, as well as various strategies chosen and practiced by individual instructors based on their own theoretical and pedagogical orientations. Future research may explore L2 writing instruction in analogical contexts more extensively through the suggestions offered in this paper.