Ms McCullough worked as a neuroscientist in the United States before turning to writing full-time.
The Thorn Birds, a romantic Australian saga published in 1977, became a worldwide bestseller and a popular mini-series in 1983.
For nearly 40 years Colleen McCullough was one of Australia's top-selling novelists.
The literary establishment may have been sniffy about her work, but McCullough laughed all the way to the bank as her tales of forbidden love, her historical series covering the fall of republican Rome and her body-filled police procedurals made her a wealthy woman.
Germaine Greer once said her early and fabulously successful work, The Thorn Birds, was the best bad book she'd ever read and compared it to Barbara Cartland's bodice-rippers.
McCullough, who died on Thursday aged 77 was born in Wellington in the central west of NSW, on June 1 1937. As a child she buried herself in books to try to escape her 'jockstrap' family.
A bright girl, she topped the NSW Leaving Certificate in English and would have been a doctor if she hadn't been allergic to the antiseptic soap that surgeons used to scrub.
She turned to neuroscience, working in the Royal North Shore Hospital and the Great Ormond Street Hospital in London before moving to the United States as a teacher and researcher in neurology at the Yale Medical School.
Towards the end of her 10 years at Yale she wrote her first two novels.
The first, Tim (1974), about a middle-aged women's romance with a good-looking, intellectually disabled handyman, did well and was made into a film starring Piper Laurie and Mel Gibson.
The second, The Thorn Birds (1977), about a priest's agonising choice of church career over love, enabled her to live where she wanted and to write full-time.
Its American paperback rights alone were worth $1.9 million and it was made into a miniseries with Richard Chamberlain, Bryan Brown and Rachel Ward.
She lived for a time in the US and London before settling on Norfolk Island, the former penal colony. In 1983, aged 46, she married Ric Robinson, a 33-year-old islander and descendant of a Bounty mutineer.
During the 1980s she wrote love stories like An Indecent Obsession and The Ladies of Missalonghi, with the latter owing a great debt to The Blue Castle by L.M. Montgomery of Anne of Green Gables fame.
In a genre change, she also wrote the post-apocalyptic A Creed for the Third Millennium.
McCullough's 1990s output was dominated by her seven-novel Masters of Rome series, published between 1990 and 2007.