Introduction:Current orthodoxy states that feedback should be timely and face-to-face, yet the optimal timing and mode of delivery for feedback is unclear. We explored what “optimal timing” means from residents’ points of view as feedback providers and receivers, to ultimately inform strategies to optimize feedback in training.Methods:As near-peers who have dual roles in both providing and receiving feedback, 16 subspecialty (PGY4 and 5) internal medicine residents were interviewed about their perceptions of the optimal timing and format of feedback. Using constructivist grounded theory, interviews were conducted and analyzed iteratively.Results:Drawing on their experiences as providers and recipients, residents described simultaneously considering and weighing multiple factors when deciding on when and how to provide feedback. These included their own readiness to engage in providing meaningful feedback, the perceived receptiveness of the learner and the apparent urgency of feedback delivery (e.g., if patient safety was at stake). Face-to-face verbal feedback was valued for encouraging dialogue but could be uncomfortable and limited by time constraints. Written feedback could be more honest and concise, and the possibility of asynchronous delivery had potential to overcome issues with timing and discomfort.Discussion:Participants’ perceptions of the optimal timing of feedback challenge current assumptions about the benefits of “immediate” versus “delayed”. The concept of “optimal timing” for feedback was found to be complex and context-dependent, defying a formulaic approach. There may be a role for asynchronous and/or written feedback, which has potential to address unique issues identified issues in near-peer relationships.