Between 1901 and 1914 he lived in London, where he gradually gained fame as a composer and piano virtuoso. His co-operation with Schott started in 1911, when the increasing recognition of his works manifested itself through performances in London Queen's Hall and the Aeolien Hall, for instance. In these days his friendship with the Norwegian composer Edvard Grieg developed. Grieg's devotion to the music of his country inspired Grainger to occupy himself with English folk music. With a phonograph he collected numerous examples of English folk music, which he later linked into his own compositions. Also, in these days, his close friendships with composers like Frederic Delius, Cyril Scott or with personalities of English music life like Herman Sanby and Balfour Gardiner developed.

In 1914, Grainger and his mother moved to the United States, where he lived until his death. Although he always saw and called himself an Australian, he became an American citizen and, for a short time, a member of the US Army Bands.

After the First World War Grainger continued his concert tours and lectures, which also led him back to Australia from time to time. In the 1930's he laid the foundation stone of the Grainger Museum at Melbourne University. In 1928, he married the Swedish artist Ella Viola Strom. Grainger also increasingly dedicated himself to the research and the publication of medieval music and the music of foreign cultures. Towards the end of his life, he worked on methods of carrying out "free music", i.e. music without any restrictions of time or determined intervals. Together with scientist Burnett Cross he developed the so-called "Free Music Machines", which were the predecessors of modern electronic synthesizers.

Percy Alridge Grainger died on 20 February 1961 in New York and was buried in his family's grave in Adelaide, South Australia.

 The International Percy Grainger Society