This study investigates the effects of prompting on secondary students' written peer feedback in chemistry investigation reports. In particular, we examined students' feedback features in relation to the use of criteria, feedback specificity, and feedback levels. A quasi-experimental pre-test post-test design was adopted. Reviewers in the prompted condition were provided with question prompts that asked them to pose written feedback to their peers on what they did or did not do well and suggestions for improvement, while reviewers in the unprompted condition gave written peer feedback without prompts. The findings showed that prompted peer feedback has a significant effect on the number of comments related to Knowledge of errors, Suggestions for improvement and Process level feedback. This study supports the view that prompting peer feedback in the use of criteria, feedback specificity and feedback levels opens up opportunity for reviewers to engage more meaningfully with peer feedback in report writing tasks.