Effects of peer response using instruction in genre knowledge on the writing of 140 sixth-grade students are investigated. In one condition students were taught specific genre knowledge involving functions of linguistic indicators of time and place. In another condition students were taught more general aspects of communicative writing. Both conditions were compared with a baseline control, receiving regular writing education. Students were randomly assigned within classrooms to each of the three conditions. The use of indicators of time and place was positively related to writing quality. Furthermore, strong effects of the specific genre knowledge condition on the use of these linguistic features in writing and revision were found. Findings indicate that instruction in specific genre knowledge is a valuable addition to writing with peer response.