An "onstage discussion" refers to a conversation or dialogue that takes place in front of an audience during a public event or performance. Full definition
I led an hour - long onstage discussion last week with two conservationists at the Aspen Ideas Festival exploring ways to manage human development to keep the Amazon rain forest thriving in this century. (dotearth.blogs.nytimes.com)
The evening will feature a post-screening onstage discussion -LSB-...] (hollywoodnews.com)
For more on the perils of overdoing the heart and gut part, read «Beware the Simple Storyteller,» Olson's assessment of a recent onstage discussion I participated in with Josh Fox, the director of the «Gasland» anti-fracking films, the actor Alec Baldwin and another journalist. (dotearth.blogs.nytimes.com)