She has appeared in several theatre productions and created the one-woman play The Height of the Eiffel Tower, which she performed at the Edinburgh Festival Fringe in 2014.
O'Reilly played Lynn Matthews in the biographical television film Billy and starred as Kylie Bucknell in the horror-comedy Housebound.
O'Reilly and her husband Peter Salmon created the comedy-thriller INSiDE, which won the International Emmy Award for Best Short-Form Series in 2021.
[3] After a stint in the comedy show A Thousand Apologies, O'Reilly was cast in a new production of Toa Fraser's play Bare.
The play focuses on Terri Hulme, a mother of four, who takes a closer look at her life when she goes on a coffee date with an old university friend.
[9] She also starred as Desdemona in Jesse Peach's production of Othello and made a guest appearance in the comedy-drama series Nothing Trivial, as lead character Mac's love interest, Alison.
[5][10] O'Reilly went on to star in the television film Safe House, which aired during TV One's Sunday Night Theatre.
[16] O'Reilly stars as Kylie Bucknell in Gerard Johnstone's horror-comedy Housebound, which had its world premiere at SXSW.
[17] For her performance as Kylie, O'Reilly earned a nomination for Best Actress at the 2014 Rialto Channel New Zealand Film Awards.
[20] The following year, she was cast as the female lead, Vanda, in the Auckland Theatre Company's production of Venus in Fur.
[25] O'Reilly also starred in comedy-thriller INSiDE, created with her husband Peter Salmon during New Zealand's COVID-19 lockdown.
[32] On 16 September 2024, O'Reilly was named as part of the cast for the Paramount+ series Playing Gracie Darling at the 2025 Channel 10 / Paramount+ Upfronts.