A descriptive longitudinal investigation of EFL academic discussion writing following systemic functional linguistics–oriented genre-based instruction

Abstract Long-term evidence on the durability of genre-based writing instruction in EFL higher education remains limited, because most studies evaluate outcomes immediately after a single course and rarely track whether genre resources are maintained or reshaped across multiple years, evidence that is important for curriculum design and program-level decision-making. This exploratory, descriptive, small-scale longitudinal classroom investigation traces the development of EFL academic discussion writing following Systemic Functional Linguistics (SFL)-oriented genre-based approach (GBA) instruction in a Japanese university context. Two cohorts of students who completed the same 15-week SFL–GBA course produced timed discussion essays at Time 1 (pre-course), Time 2 (immediate post-course), and Time 3 (delayed posttest 3–4 years later). To contextualize Time 3 performance under matched task conditions, a third cohort who completed a skill-based writing course completed the same Time 3 task and served as a cross-sectional reference group. Fifty-eight essays were analysed using mixed methods that combine corpus-based lexical indices (text length, lexical richness, and academic vocabulary use) with SFL-informed coding of discussion-genre resources. Across the SFL–GBA learning communities, several lexical and genre-related resources observed at Time 2 were broadly maintained at Time 3, while some interpersonal resources showed mixed trajectories, highlighting areas that may require sustained instructional support beyond the first year.