Omer Call Stewart was born in 1908 in Provo, Utah. He grew up in a LDS (Mormon) family and environment, and from 1928 to 1932 he served a French speaking mission for the Church of Jesus Christ of Latter-day Saints (LDS Church). He later withdrew from membership in the LDS Church, but maintained a strong interest in the subject of religion. Stewart earned his B.A. from the University of Utah, completing work for the degree in 1933. He studied anthropology and spent two summers in the field under the direction of Dr. Julian H. Steward. While at the University of Utah, he was chosen to play the lead male role in the varsity play "Mis' Nelly of N'Orleans," directed by Maud May Babcock. The lead female role was played by Wanda Clayton, whom Stewart married a few months after the play was performed. In 1934, Clayton and Stewart were divorced. He later married Lenore Thurston, with whom he had four children. Stewart's graduate education took place at the University of California, Berkeley, where he completed his Ph.D. in anthropology in 1939.

During his time at Berkeley, Stewart had his first experience with the peyote ceremonies of the Native American Church. These ceremonies became a major focus of his work in later years. Stewart spent most of his professional career at the University of Colorado at Boulder, where he was responsible for the formation of the University's Department of Anthropology. He invested much time and effort into protecting the rights of Native Americans. Such work included research and service as an expert witness in land claims cases and cases involving religious freedom and the use of peyote. Stewart earned Emeritus status at the University of Colorado. He was the author of a number of articles and other writings, most of which address Native American issues. He received many awards, fellowships and grants, and was a member of a number of professional societies. Stewart died in Boulder, Colorado, in 1991.