I'm not exactly sure if this is what you are asking, as we do not use the terms "QI" or "peer review" in our department, but here goes:
The atmosphere at my residency program is relaxed and informal; our staff show tricky and/or interesting cases around a lot. I think the only times than an audit is technically "required," however, is on new cancer diagnoses and for uterine cervix-Pap smear correlations (usually we bug whichever cytopathologist signed out the Pap). In our old LIS you could freehand information in the audit section (i.e. you could specify that you showed Dr. so-and-so slides x, y and z), but the new one only lets you list the name of the staff who audited the case, which I don't think is ideal.
We don't have a specific conference or time of day during which this occurs. People just randomly pop into each others' offices to show cases as necessary. Everyone is used to this and the vast majority of the attendings are very patient and don't mind dropping what they are doing to give a quick audit.
We also periodically have "practice-based learning" conferences during which cases in which an error was made (or was nearly made, could easily have been made, etc.) are reviewed and discussed.