Although peer interaction has received attention in second language (L2) collaborative writing (CW) research, the manner and quality of peer interaction have been less investigated. Previous studies usually examined peer interaction by looking at language-related episodes, overlooking the ways students negotiate for different types of knowledge for successful writing, such as content, organisation, and discourse. Moreover, the association between quality of negotiation and students' writing process is elusive. This study aims to examine the way students discussed different aspects of writing during interaction and explore the impact of quality of negotiation on students' subsequent writing and revisions. Data were collected from an intact academic writing class at a New Zealand university, where students formed groups to produce a single text per group over 12 weeks. Results showed that students discussed content and organisation more than language, and different qualities of negotiation were associated with different writing and revision outcomes. In addition, students discussed both local and global aspects of writing, and quality of negotiation is an important factor that mediates students' writing and revision behaviours.