From Longman Dictionary of Contemporary Englishonstageon‧stage /ˌɒnˈsteɪdʒ◂ $ ˌɑːn-. ˌɒːn-/ adjective, adverb on the stage in a theatre OPP offstage Even today I get nervous before I go onstage.
Examples from the Corpus
go onstage• To go onstage in the flag is to be a 50p magnet, nomatterwhat it might mean in an ideal world. 