Not just her thousands of works - it is estimated she created more than 10,000 paintings and drawings in her six-decade career - that her art dealers and friends knew about.

When her friends moved to empty her house they made a surprising discovery.

More works, never before seen, were found hiding behind cupboards, hanging in disused rooms, wrapped in paper stuffed behind something.

They were works that Olley had possibly done for herself, possibly wanted to come back to complete, possibly forgotten about herself.

But now they will hang, for the first time ever, in a new exhibition at Philip Bacon Galleries in Brisbane. It will be the last exhibition of new Olley works ever.

She was one of Australia's most beloved and prolific artists. The exhibition canvasses her career from some of her earliest works - including a painting from 1948 of the old Masonic Hall in Alice Street, right through to the piece Olley completed on the day she died.

Her dear friend and fellow artist Ben Quilty, who was in Brisbane to open the exhibition, said it was an extraordinary survey of her career.

"There was so much work, her house became this vault of things," he said.

"She just produced and produced and produced and Philip has gone through that vault and curated this show.

"It's amazing to see, through her eyes, how the city of Sydney changed, see how she grew as an artist, it's really extraordinary."

While the collection on display at Philip Bacon is vast, it is a small sample of what Olley created in her life.

"I have always thought there would be an interesting show if you could put all of her life's work out," Quilty said.

"She didn't stop right until the day of her death and during her career she suffered from chronic depression so she had fabulous times and then followed that with really dark times.

"That darkness is reflected in the works she was creating at the time, because she didn't stop.

"They aren't lesser paintings but they become imbued with this solemn heavy feeling of the depression.

"If you put all her works in a row it would be like a rainbow serpent with the darkness and then back into the light."

Olley's legacy wasn't just in the work she created but in the knowledge, experience and drive she shared with other artists that she would hand pick to mentor and champion the careers of.

Quilty was one of those artists.

She bought the first Quilty piece that would hang in a major art museum.

"It was kind of a back door way in really," he said.

"She bought my painting at an exhibition in Melbourne then bullied the curators at the New South Wales Art Gallery to take it into the collection."

But Olley didn't give her time, experience and mentorship lightly.

"When you have someone like Margaret Olley on your side, it was a very positive force," Quilty said.

"But with that support came great expectation.

"She wanted me to do well, she expected me to work hard, she was very demanding of me."

The expectations and demand helped shape Quilty into the award-winning artist he has become, and he now acknowledges that he must continue Olley's own legacy.

"It sounds wanky, it feels wanky to be talking about it," he said.

"When I first had that attention from Margaret Olley, I was 29 and won the Brett Whiteley Travelling Scholarship

"In my very first conversation with her, and it was a whirlwind of a night, I remember it so clearly, she said she has expectations of me in my practice and my work, and 'when you are my age I want you to be helping people as I am helping you now'."

He has lived up to those expectations.

From mentoring executed Bali Nine drug dealer Myuran Sukumaran as he explored visual storytelling through painting, to sharing his passion for art with everyone from people in the street to prime ministers, he is determined to ensure her legacy carries on.

"It did leave a huge hole for a number of us because she was this person looking over all of us," Quilty said.

"We were the ducklings and she was the mother duck.

"They are big footsteps to follow in but there is a whole league of people who are determined to follow in that way of being generous and supporting arts and supporting culture and pushing it in the face of the people who need to see it most."

The Margaret Olley exhibition is on now at Philip Bacon Galleries.

The collection includes a range of never-before seen works along with several of her most significant pieces that are available to the public.

Visit philipbacongalleries.com.au for full details.

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