During a return visit to New Zealand in 1907-9, he held solo exhibitions in Wellington and Christchurch, and participated in art society shows. He met Dorothy Kate Richmond, the doyenne of the Wellington art scene, and her nephew Esmond Atkinson, who was also a painter. Merton re-enrolled briefly at the Canterbury College School of Art in 1908.
In 1909 he returned to London, where he studied with the Flemish-born painter Charles van Havermaet in 1909-10, and made extended working visits to the Netherlands, Cornwall and Brittany. On this last occasion he participated in a sketching class at Concarneau, taught by Frances Hodgkins. He also travelled in other parts of western France in the summer of 1910.
Merton was elected to membership of the Royal Society of British Artists in 1910, and showed works in their 1910 and 1911 exhibitions. He continued to exhibit works in New Zealand until the late 1920s and was represented in several group shows in England and France between 1910 and 1926.
During an extended period in which he was based in Paris (1910-3) he studied first at the Académie Colarossi, then in the studio of Percyval Tudor-Hart where fellow-New Zealander Maud Sherwood was also studying. It is there that he met Ruth Calvert Jenkins, an American art student whom he married in London in 1914. In these years he made excursions to Northern Spain, England and Italy.
Ruth and Owen Merton lived from mid-1914 to mid-1916 in Prades, southern France, where their first son, Tom, was born in 1915. Owen played the piano in charity concerts and perhaps in the local cinema and refused to enlist after war was declared.
The family moved to New York in 1916, and Owen was based there until 1923. Their second son, John Paul, was born in 1918 and Ruth Merton died in 1921. Owen may have lived for a time as a farm worker and he certainly worked as a professional landscape- and garden-designer, church organist and cinema pianist. He exhibited in numerous group and solo shows, including some important curated exhibitions, in New York and Philadelphia in the period 1917-1925 and was clearly considered by his peers to be a serious member of the New York avant-garde.
In the years 1921-3, after his wife's death, he visited Bermuda (twice) and Cape Cod (once). He was given a solo exhibition in the prestigious Daniel Gallery, New York, in 1923.
Meanwhile he had met the American writer Evelyn Scott in Bermuda, in late 1921 or early 1922, and lived with her until 1925. He became the basis for characters in several of her novels.
He made an extended visit to Europe (Italy, France, England) in 1923-5, and also spent some months of the winter of 1923-4 in Algeria. He had a solo exhibition at the Leicester Gallery, London, in 1925, and a second solo exhibition in New York (Daniel Gallery) also in 1925.
After a brief visit to New York in the summer of 1925, he returned to Europe for the last time, accompanied by Tom.
They settled in Saint-Antonin, south-western France, where he bought land and built a house. Owen travelled widely in southern France to paint, he played the piano in the Saint-Antonin cinema and was president of the local rugby club.
His second solo exhibition in London was held in 1928 and he was based in England thereafter (with at least three short visits to France), although his house would not be sold until 1930.
Owen Merton died in London in 1931 after a prolonged illness.