In undergraduate natural science courses, two types of evaluators are commonly used to assess student writing: graduate-student teaching assistants (TAs) or peers. The current study examines how well these approaches to evaluation support student writing. These differences between the two possible evaluators are likely to affect multiple aspects of the writing process: first draft quality, amount and types of feedback provided, amount and types of revisions, and final draft quality. Therefore, we examined how these aspects of the writing process were affected when undergraduate students wrote papers to be evaluated by a group of peers versus their TA. Several interesting results were found. First, the quality of the students' first draft was greater when they were writing for their peers than when writing for their TA. In terms of feedback, students provided longer comments, and they also focused more on the prose than the TAs. Finally, more revisions were made if the students received feedback from their peers-especially prose revisions. Despite all of the benefits seen with peers as evaluators, there was only a moderate difference in final draft quality. This result indicates that while peer-review is helpful, there continues to be a need for research regarding how to enhance the benefits.