This paper aims to explore advanced ESL learners' ability to make improvements in grammatical accuracy by autonomously noticing and correcting their own grammatical errors. In the recent literature in SLA, it is suggested that classroom tasks can be used to foster autonomous language learning habits (cf. Dam 2001). Therefore, it is important to consider classroom tasks that encourage autonomous language learning behaviour. Working with 13 advanced ESL composition students, we engaged the subjects in an explicit task in which they compared their own use of grammatical form in their own written output to the use of grammatical form as used in a text written by a native speaker. Based on the comparison between their own written output and the native speaker text, subjects subsequently corrected their grammatical errors. Results suggest that such a comparison task is beneficial in allowing learners to make gains in grammatical accuracy.