Ordained priest in 1821, and subsequently professor and director of the two seminaries, minor and major, of his diocese, in 1834 he established the Institute of Auxiliary Priests, with the aim of assisting parish priests through parochial retreats, preaching, missions, etc.; urged by the bishop of Le Mans, he took charge, in the same year, of reorganizing the Congregation of the Brothers of St. Joseph, founded in 1820 by Fr. G. F. Dujaríé, and ended by merging the two groups into a single Congregation (11 March 1837), which took the name of St. Cross, and received the decree of praise on 18 June 1835 and the approval of its Constitutions by the Holy See on 13 May 1857. Moreau saw his work prosper greatly, especially in France and America; he devoted himself with enthusiasm to education, preaching particularly in rural areas and in foreign missions, parochial ministry, good press, and the direction of homes for delinquent or abandoned boys. To him is also due the foundation, in 1841, of a parallel female institute, the Sisters of St. Cross, with the purpose of attending especially to the education of young women.
Besides the circular letters addressed to his religious (2 vols., Montréal 1941), he wrote Meditations for religious and laity (ibid. 1932) and several pedagogical works of high value. Indeed, together with Lacordaire, Montalembert, and Dupanloup, he was one of the most effective and steadfast pioneers in the struggle for the freedom of education, succeeding in opening a flourishing college at Le Mans even before the law on educational freedom was passed. He was given by Pius IX the title of “Apostolic Missionary.” The cause of his beatification has been introduced.