Engaging students in peer reviewing in the writing classroom has been widely practiced as a way of assessment for learning. In-depth research is needed however to investigate how students specifically use peer comments in their editing process. Using a corpus-based approach, this article investigates the acquisition of journalistic writing skills by 112 undergraduates in Hong Kong. The learner corpora comprise student comments and self-reflections from an online news writing project. While grammatical accuracy remains to be a concern for effectiveness of the peer review practice, the findings reflect sound understanding of structure, layout and style of the online news genre among the participants. Although the students commented more on contents and organization of news writing, findings from keyword search and co-text in the concordances demonstrate awareness of main features of the online news genre. The findings further clarified judgement and choices made by the ESL learners during the drafting and editing processes. The study suggests how peer assessment and self-assessment can be effectively practiced through a cycle of reviewing peer writing, receiving peer comments and self-reflecting on their own drafts. It also indicates how peer review may help acquisition of style and lexico-grammar which can be demanding for many ESL learners.