This article investigates the role of direct corpus use in learners' collocational competence in academic writing. An experiment was conducted between two groups of Chinese postgraduates who had no previous knowledge of corpora. It was embedded in a regular 4-month linguistics course in the students' programmes, where a corpus-assisted method was used for the experimental group and a traditional, or rule-based, method was used for the control group. The English essays written by these two groups of learners from different time periods (before, immediately after, and two months after the course) were analysed regarding the learners' collocational use--in particular, verb-preposition collocations. The results reveal that while both groups showed improvements in their academic writing, the students in the experimental group displayed a significant improvement in the use of collocations, including a higher rate of accuracy, or naturalness, and an increased use of academic collocations and fixed phraseological items. It is thus concluded that the knowledge and use of corpora can help students raise their awareness of habitual collocational use and develop their collocational competence. This supports the positive role of direct corpus application in an EFL context.