On leaving school she had a gap year job as a human resources (HR) adviser working with Bechtel on the Kinleith Mill modernisation project, then completed an honours degree in resource and environmental planning at Massey University. Bechtel honoured an earlier job offer and she wound up spending a year and half focusing on continuous improvement and HR issues for a major construction project in Queensland.
On her return, she joined Te Puni Kokiri where she spent five years, mostly based in Whakatane working on issues involving Maori land development in the eastern coastal area.
After a period in the private sector, she joined the Raukawa Charitable Trust in 2005, ending up with three key roles, treaty negotiations, external governance, particularly in treaty and the land and water areas, and developed and ran the trust's environmental group.
Ms O'Sullivan also developed her own expertise in governance and leadership. She represented New Zealand in 2006 at the first Emerging Pacific Leadership Conference, was selected to do the one year Kellog Rural Leadership Course through Massey in 2008, and in 2012-13 was the inaugural observer director on the board of AgResearch. She also served for several years on the Waikato River Authority, and on the Waikato River Trails Trust, and was the first woman to chair a major catchment committee for the Waikato Regional Council.
However, after a decade with Raukawa, Ms O'Sullivan was looking to take the new step and took up the Ngati Ranginui role. While it was a different iwi from the one she had worked so closely with, there were close whakapapa connections with Raukawa, she said.
"My passion is contributing to Maori Inc as part of the NZ Inc story and development," she said. "Tauranga is a very attractive place to come to. What really resonated with me about Ngati Ranginui, were the values they demonstrate and where the board wanted to go."
The iwi has almost completed its settlement process, which is currently awaiting the final legislative steps.
"The board members wanted to refresh our strategy and make sure the organisation is fit for purpose in the post-settlement environment. We want to make sure we deliver value for the wider community and our mokopuna of the future. We will do this through partnerships and collaboration."
Steve Saunders, managing director of Tauranga's Plus Group of agri-tech companies, who is of Ngati Ranginui (Ngai Te Ahi) lineage, is deeply involved in Maori horticultural development through his directorship of Tuhono Whenua Horticulture, and is also on the board of crown research institute Landcare Research.
"I've only known Steph for a short time, but have found her vision and passion for iwi inspiring."
Mr Saunders illustrated her contribution by quoting the old Maori saying: " He aha te mea nui o te ao. He tangata, he tangata, he tangata [What is the most important thing in the world? It is the people, it is the people, it is the people]."