After her family migrated to Australia she was brought up and educated in Sydney, where she took Irish dance lessons with Joy Ransley and Valerie McGrath.

[1][2] O'Connor had joined a touring dance troupe by August 1974, which travelled to Ireland, Paris, London, and the United States west coast.

[7] Other British theatre credits include, A Chorus Line,[7] Cabaret,[7] Hot Stuff, Chicago, Damn Yankees, West Side Story and as Ellie May in Show Boat for the Royal Shakespeare Company and Opera North in 1989.

The entertainer returned to Australia by February 1994, where she took the role of Anita in a national tour of West Side Story, performing in Melbourne, Adelaide and Sydney and then Auckland in New Zealand.

O'Connor's musical film work includes the role of Nini Legs in the Air in Baz Luhrmann's Moulin Rouge!

O'Connor starred as Judy Garland in the 2005 world premiere of Peter Quilter's play, End of the Rainbow, at the Sydney Opera House.

[11] The number was reprised in Williams' arrangement for her shows at the Garrick Theatre 2010 season of The Showgirl Within,[12][13] and for the opening in 2012 of Hamer Hall, Melbourne.

[16] In March 2009 O'Connor reprised her role as Kelly in the 2009 Australian production of Chicago where she starred alongside Craig McLachlan and Gina Riley.

[17][18] In May 2011 she starred as Mrs Lovett in the Théâtre du Châtelet production of Sondheim's Sweeney Todd: The Demon Barber of Fleet Street in Paris,[19] with David Charles Abell as musical director.

From April 2017 through to March 2018, O'Connor played Countess Lily in the musical, Anastasia, at the Broadhurst Theatre on Broadway, New York.

[29] O'Connor began 2019 by starting in the critically-acclaimed and sold-out Darlinghurst Theatre Company production of The Rise and Fall of Little Voice (directed by Shaun Rennie).

She followed this with a staged concert of the rarely performed musical Applause at Hayes Theatre, playing the leading role of Margo Channing.

[30][31] In May 2024, O'Connor reprised her 2018 role as The Old Lady in Candide in a co-production by the State Theatre Company South Australia (STCSA) and State Opera South Australia, performed for three nights in Her Majesty's Theatre, Adelaide, under the direction of Mitchell Butel, who was now STCSA artistic director.