Barker received a degree in religion from Azusa Pacific University and was ordained to the ministry by the Standard Community Church, California, in 1975. He served as associate pastor at several churches: Religious Society of Friends (Quaker), a church in the Assemblies of God fellowship, and an independent Charismatic church. He receives royalties from his popular children’s Christian musicals, Mary Had a Little Lamb (1977) and His Fleece Was White as Snow (1978), both published by Manna Music.

In 1984 he announced to his friends, family, and co-ministers that he became an atheist, and appeared on AM Chicago (hosted by Oprah Winfrey) later that year on a show about “kicking the religion habit”.

Barker and Gaylor met when both were guests on the show. They began dating six months later and married in 1987. They have a daughter, Sabrina Delata.

He is a member of the Lenni Lenape (Delaware Indian) Tribe of Native Americans, and in 1991 edited and published Paradise Remembered, a collection of his grandfather’s stories as a Lenape boy in Indian Territory.

He is the current co-president with his wife Annie Laurie Gaylor of the Freedom From Religion Foundation, an American freethought organization that promotes the separation of church and state. Barker is co-host of Freethought Radio, a radio program based in Madison, Wisconsin for atheists, agnostics, and other freethinkers that began in 2006 and has included interviews with Richard Dawkins, Sam Harris, Steven Pinker, Christopher Hitchens, Philip Pullman, Daniel C. Dennett, Julia Sweeney, and Michael Newdow.