Purpose: Peer review (PR) is an important component in ensuring high-quality lung radiotherapy (RT) plans. However, there are inconsistencies in the extent, timing, and minimum requirements for PR. We sought to develop guidelines of best practices for PR in curative lung RT through an expert consensus process., Methods: A modified Delphi process was conducted that consisted of an initial review by a dedicated steering committee followed by a pan-Canadian, multidisciplinary Delphi panel with 3 rounds (premeeting survey, face-to-face meeting, and postmeeting ratification survey). Candidate PR elements were ranked by importance and stratified by treatment of locally advanced (LA) disease with conventional RT or stereotactic ablative body RT (SABR) for early-stage disease., Results: For the LA case, 6 elements (indications for RT, gross tumor volume [GTV], clinical target volume [CTV], internal target volume [ITV], dose/fractionation, and normal lung dosimetry) were considered as essential PR elements. Of these, 90%-100% of the panel endorsed them to be important to PR, and 80% believed that the PR should be done by a second radiation oncologist (RO). In the SABR case, 6 PR elements (indications for RT, GTV, CTV/ITV, organs at risk contours, dose/fractionation, and composite plan review) were deemed essential. Of these, 90%-100% of panel members believed these elements to be important to PR and unanimously agreed that PR should be done by a second RO., Conclusion: A suite of PR elements for lung RT has been developed and endorsed with high consensus. This suite should serve as a basis to help to harmonize PR practices across centers and to help to develop novel PR approaches going forward.