Collins was born in Des Moines, Iowa, the son of Madeleine (née Robertson) and Cyrus S. Collins, an airline executive. Collins is the great-great-grandson of General James Baird Weaver, the 1880 Greenback Party presidential candidate and the 1892 Populist Party ("People's Party") candidate for president. Collins was raised with his two older brothers in Hastings-on-Hudson, New York and attended Amherst College, graduating cum laude. He played bass guitar and rhythm guitar in a number of rock and roll bands at Amherst, including Tambourine Charlie & The Four Flat Tires, The Naugahyde Revolution (with Jim Steinman, then a fellow student, on keyboards), and The Flower & Vegetable Show (he has played his guitar on “7th Heaven,” “It's Always Sunny in Philadelphia,” and in the 2007 romantic comedy “Because I Said So”).

Collins is best known for his role as the Reverend Eric Camden in more than 200 episodes of the television series “7th Heaven,” though he also notably portrayed Captain/Commander Willard Decker in “Star Trek: The Motion Picture.” Reverend Camden's wife, Annie, is played by fellow Star Trek alum Catherine Hicks (she played Dr. Gillian Taylor in “Star Trek IV: The Voyage Home”). Additional television credits include Jake Cutter in the cult favorite “Tales of the Gold Monkey and Tattingers,” as well as guest appearances in “The Waltons,” “Barnaby Jones,” “Charlie's Angels” and numerous mini-series and made-for-television movies. He was nominated for an Emmy Award for his work opposite Ann-Margret in the mini-series “The Two Mrs. Grenvilles” and he played John F. Kennedy in the mini-series “A Woman Named Jackie,” which won the Emmy for Best Miniseries.

Collins is married to actress Faye Grant. They have been married since April 21, 1985 and they have a daughter, Kate. He is an Episcopalian. He is also a practitioner of Transcendental Meditation and has engaged in the advanced Yogic Flying technique since 1980. He is a national co-director of the Committee for Stress-Free Schools, which advocates practicing TM in schools and funds TM research.