Adopting the approaches of "pattern hunting" and "pattern refining" (Kennedy & Miceli, 2001, 2010, 2017), this study investigates how seven freshman English students from Taiwan used the Corpus of Contemporary American English to discover collocation patterns for 30 near-synonymous change-of-state verbs and new ideas about the topic of "change" in the drafting stage of their essay writing. The study used a mixed-methods approach to examine the learning outcomes, learners' corpus use, and their perceptions of the process. Results were drawn by analyzing writings in three time frames (pre-test, post-test, delayed posttest), video files of corpus consultation, questionnaires, and stimulus recall-session interviews. The results showed that the learners successfully discovered and incorporated collocation patterns in change-of-state verbs and ideas about the topic of change into their essays, although some difficulties emerged. Their performance on change-of-state verbs improved, and this improvement remained three months after the treatment. The study also demonstrated learners' different perceptions and actualizations of the affordances offered by the corpus. While all learners used the corpus to correct collocation errors, they had diverse attitudes and uses of the corpus to address content ideas or collocation complexities in their writing. The study concludes by discussing the theoretical and pedagogical implications of the results.