As a career, Reiser was the manager of the Deseret Book Company in Salt Lake City.
Beginning in 1921, David O. McKay selected him to be the secretary to the general superintendency of the Deseret Sunday School Union, a position he would hold for over 20 years.
During his time in the Sunday School, Reiser wrote a variety of books and lesson manuals, including a 1945 history of the LDS Church for children.
Reiser served in the Sunday School until 1952, when he was asked to become the president of the British Mission of the church.
During his time in England, Reiser organized the church's purchase of the property for the construction of the London Temple.