She also taught privately.
Long's husband, Joseph de Marliave (1873–1914), was killed in August 1914 in action during World War I.
Maurice Ravel dedicated the last section, the Toccata, of Le tombeau de Couperin to him.
Marguerite Long gave the first performances of this work in 1919, and in January 1932 the premiere of Ravel's Piano Concerto in G major, which was dedicated to her, followed shortly by its first recording with Ravel conducting.
In 1943 she and violinist Jacques Thibaud established the Marguerite Long-Jacques Thibaud International Competition for violinists and pianists, which takes place each year in Paris.
19 with the Orchestre National de France under Charles Munch.
The centrepiece was the first performance of a collaborative orchestral suite written in her honour by eight French composers, titled Variations sur le nom de Marguerite Long.Marguerite Long died in Paris in 1966, aged 91.