This study aims at a rediscovery of the extent to which a Data Driven Learning (DDL)-based intervention could become instrumental in facilitating grammar instruction with a specific focus on English for Academic Purposes (EAP) and learner autonomy in a preparatory program comprised mostly of Turkish-L1 learners. It provides a context-restricted longitudinal depiction of the effectiveness of a DDL-based grammar instruction endorsed by teacher mentorship across groups asynchronously, thus re-testing the limits of DDL-oriented corpus pedagogy in contexts where a control group is not available. To this end, a corpus was compiled out of the existing reading and listening materials in use ad hoc as the Alternative Corpus of Academic Texts (ACAT), and a total of 19 grammar lessons covering topics in the curriculum of the second level of the grammar course were developed using the ACAT. Blind pre- and post-test procedures were administered with all four experimental groups independent of each other to gradually build up an understanding of the governing pattern of learner achievement through DDL and corpus-based teacher-prepared materials. The analysis demonstrated a rise in student achievement across all groups despite the lack of a teacher disseminating knowledge to students DDL-enhanced teaching. With the design being unorthodox, this study shows that the triple powers of DDL, self-discovery, occasional teacher supervision, in class in the traditional sense, thus showing that a sense of autonomy could be fostered through and corpus-based teaching materials, could help learners survive autonomously no matter how hectic the curriculum run at an institution is. Further research is needed to deepen this insight so that this sort of DDL practice could be implemented at an institutional level.