The phenomenon of overused adjectives by non-native speaking learners (NNS) has been pinpointed by recent research. This study designed five online units for increasing students' awareness of underused specific adjectives for EFL college writing. Five units were developed for five identified overused adjectives: "important", "beautiful", "hard", "deep", and "big". In each unit, data-driven learning materials, incorporating a bilingual collocation concordancer "TANGO", first had learners engaged in distinguishing synonymous adjectives from concordance lines as their first task. Then three exercises for practise followed as a second task. Nineteen English majors in a college freshman writing class participated in the study. The assessment measures included three tests, two in-class writing tasks, and questionnaires. The findings indicate that, in addition to improvement in the immediate posttest, students' word knowledge for synonym use was still retained as measured two months later in the delayed posttest. Moreover, in the post-instruction writing task, students avoided using general adjectives, tried to apply more specific items, and thus improved their overall writing quality. As for students' attitude toward the learning units, over half reported that inductive learning was beneficial although they still found it difficult to verbalize differences among semantically similar words. "TANGO" was also considered a useful tool for learning synonyms and their collocates. (Contains 7 tables and 2 figures.)