Teachers often complain about the quality of students' written essays in higher education. This study explores the relations between scripted online peer feedback processes and quality of written argumentative essay as they occur in an authentic learning situation with direct practical relevance. Furthermore, the effects of the online argumentative peer feedback script on students' written argumentative essay are studied. A pre-test, post-test design was used with 189 undergraduate students who were assigned to groups of three. They were asked to explore various perspectives, and the 'pros and cons' on the topic of 'Genetically Modified Organisms (GMOs)' in order to write an argumentative essay in the field of biotechnology. The findings reveal that successful students and groups differ in terms of their feedback quality than less-successful students and groups. This implies that when students engage in high-quality, elaborated and justified peer feedback processes, they write high-quality argumentative essays. Furthermore, the results show that the online argumentative peer feedback script enhances the quality of students' written argumentative essay. Explanations for these results, limitations, and recommendations for further research are provided.