Peploe was 43 years old when WWI was declared. He was called up for service but was declared unfit. He made the first of several trips to Kirckudbright in 1915, applying the lessons he had learnt in France to images of the town and the surrounding countryside. Back in the studio, Peploe applied himself to a rigorous investigation of the work of Cézanne, as seen in a series of monumental still lifes. Following Cadell’s demobilisation in spring 1919, he and Peploe worked closely together, influencing each other’s work and even sharing props.
The end of the war seems to have inspired Peploe to begin the series of still lifes for which he is best known, and which were to occupy him until about 1923. Gone was the bravura and un-diluted colour of the pre-war paintings and in its place came a serious, methodical study of the genre. Peploe obsessively arranged and re-arranged a cast of props centred first on tulips and later on roses in Chinese porcelain vases, surrounded by objects including fans, books and fruit in compotiers, often set before draped backgrounds and depicted in a high-key palette.
In 1920 Cadell introduced Peploe to the Hebridean island of Iona; they returned virtually every summer for more than a decade. Peploe was particularly taken with the north end of the island and the views from it over to Ben More on neighbouring Mull. He also worked in Cassis in the south of France alongside Cadell in 1924 and returned by himself in 1928 and 1930. In 1928 he painted in Antibes with Hunter.
During the 1920s Peploe’s reputation grew steadily. In 1915 he had his first solo exhibition at La Societé des Beaux-Arts, Alexander Reid’s gallery in Glasgow. Throughout the 1920s there were regular exhibitions in Glasgow and Edinburgh, as well as in London later in the decade, invariably accompanied by positive press and healthy sales. Peploe had a solo exhibition in New York in 1928 and was included in important group exhibitions in London and Paris. In 1924 a landscape painting was acquired for the French national collection and in 1927 Peploe was elected a member of the Royal Scottish Academy.