It was not until he approached middle life that he began to write hymns. In 1880 Hosmer, Gannett and James Vila Blake compiled and edited "Unity Hymns and Chorals for the Congregation and the Home", a hymnbook which had a considerable circulation in its day and of which a revised edition was brought out in 1911. In 1886 Hosmer and Gannett published "The Thought of God in Hymns and Poems", a book which contained fifty–six pieces by Hosmer. The English hymnologist Percy Dearmer described Hosmer’s hymn, “O Thou in all thy might so far,” as “this flawless poem, one of the completest expressions of religious faith.” About Hosmer’s hymn “Thy kingdom come—on bended knee/ The passing ages pray,” (written for the 1891 Commencement of the Meadville Theological School), Dearmer wrote, “one of the noblest hymns in the language.” Hosmer often wrote hymns for special occasions, the most notable instance being his great hymn “O prophet souls of all the years,” written for the Parliament of Religions held in Chicago in 1893, to capture the vision and spirit of that watershed meeting. It has been said of Frederick Hosmer that he "...was a man of highest ethical standards and keen religious insight. He was never married, but he was a beloved friend and a delightful companion who could entertain with witty impromptu verse as well as illuminate conversation with profound thought. Esteemed as he was as a parish minister, his hymns were the great and lasting contribution which he made to the religious life of his time."