In 1852 Margaret Wilson moved to London, where she married her cousin, artist Francis William Oliphant. Her work continued unabated, and she produced several novels for serialization in Blackwood's Magazine, including A Quiet Heart (1854), Zaidee (1856) and The Athelings (1857). She was soon earning a steady income from her work, which she was to need after her husband died in 1857, leaving her in debt and with three children to provide for. Between 1861 and 1878 she embarked on an ambitious series of novels on English provincial life, which was to include some of her most accomplished work. The seven novel series, entitled 'The Chronicles of Carlingford', was closely Modeled on Anthony Trollope's Barsetshire novels, and bore similarities in concerns and themes to George Eliot's works. The series included Salem Chapel (1863), The Rector and The Doctor's Family (1863), The Perpetual Curate (1864), and her best known work, Miss Marjoribanks (1866). The final novel in the series, Phoebe Junior: A Last Chronicle of Carlingford, was published in 1876. 

In 1864, her daughter died, and soon after Margaret Oliphant took charge of three of her widowed brother's four children. This, plus a strain of supporting her two remaining children, took its toll on her writing. After1866 her work never achieved the same critical success of her earlier efforts. By the time of her death, Margaret Oliphant had produced over 100 novels, almost 30 works of non-fiction and over articles for Blackwood's Magazine.