[6] The Grau family immigrated to the United States in 1854 when Maurice was five years old,[7] settling in New York City where Emmanuel and Rosalie operated a boarding house.

[7] His uncle was appointed director of the Academy of Music in New York in 1862, but after a difficult tenure there during the American Civil War he left to take over the management the Theatre Français in 1866.

[9] At this time Maurice began working for his uncle in more serious theatre business endeavors at the age of seventeen,[5][3] and in 1872 he ultimately decided to not pursue the legal profession but embrace a career in artist management.

[5][7] Their partnership resulted in the first significant achievement of Grau's career: bringing the French soprano Marie Aimée to the United States.

[7] Grau made a large amount of money when he brought a French theatre troupe led by Paola Marie and Victor Capoul to the United States in a highly successful tour in 1879.

[1] Other prominent European artists he brought to the United States included actors Benoît-Constant Coquelin,[1] Jean Mounet-Sully,[1] and Henry Irving;[1] and actresses Sarah Bernhardt, Gabrielle Réjane, and Jane Hading.

[1] Grau's collaborative relationship with fellow theatre managers and producers Henry Eugene Abbey and John B. Schoeffel extended to as early as 1882.

[2] In the same year he played a significant though unofficial role in the newly created Metropolitan Opera in New York when Abbey served as the Met's first managing director.

[15] In 1887 Grau joined forces with Schoeffel and Abbey to organize a tour featuring the French stage actress Sarah Bernhardt.

The three men successfully implemented this shift, although during the six years that they co-managed the Met they also slowly brought German repertory back into its performance rotation.

[10] Poor health caused Grau to announce his retirement from the Metropolitan Opera in 1902, stating that he would end his career at the conclusion of the 1902–1903 season.