The Canadian Institutes of Health Research (CIHR) commenced a Quality Assurance Program in 2019 to monitor the quality of peer review in its Project Grant Competition Peer Review Committees. Our primary aim was to describe the performance of CIHR grant peer reviewers, based on the assessments made by CIHR peer review leaders during the first 3 years of the Research Quality Assurance Program. All Peer Review Committee Chairs and (or) Scientific Officers who led peer review for CIHR in 2019, 2020, and 2021 completed Reviewer Quality Feedback forms immediately following Peer Review Committee meetings. The form assessed Performance, Future potential, Review quality, Participation, and Responsiveness. We summarised and descriptively synthesised data from assessments conducted after each of the four grant competitions. The performance of peer reviewers on 4438 occasions was rated by Chairs and Scientific Officers. Approximately one in three peer reviewers submitted outstanding reviews or discussed additional applications and one in 10 demonstrated potential as a future Peer Review Committee leader. At most, one in 20 peer reviewers was considered to have not performed adequately with respect to review quality, participation, or responsiveness. There is a need for more research on the processes involved in allocating research grant funding.