(written from a Production point of view)
He is currently best known for his role as Reverend Eric Camden on the television series 7th Heaven, which concluded its eleven season run in May 2007. Co-starring with him as his wife on this series was Catherine Hicks, the actress who played Gillian Taylor in Star Trek IV: The Voyage Home; the show also starred TNG and DS9 guest star Christopher Michael. His father-in-law on the series was played by TNG guest actor Graham Jarvis.
An alumnus of Amherst College, Collins made his film debut only three years before Star Trek: The Motion Picture was released, with a supporting role in the highly acclaimed drama All the President's Men. Co-starring in this film were fellow Star Trek alumni F. Murray Abraham, Gene Dynarski, Richard Herd, Nicholas Coster and Paul Lambert. He went on to co-star with Michael J. Pollard, Richard Cox, and Robert Costanzo in 1977's Between the Lines, and, in the same year Star Trek: The Motion Picture was released, he co-starred with fellow Star Trek movie performers Bibi Besch and Laurence Luckinbill in The Promise.
Other film credits include Loving Couples (1980, with Sally Kellerman and John de Lancie), Jumpin' Jack Flash (1986, co-starring Whoopi Goldberg), and a cameo in The Big Picture (1989, with Michael McKean and Teri Hatcher). More recent films include The First Wives Club (1996), Drive Me Crazy (1999), and 2003's The Commission, in which he co-starred with the likes of Jim Beaver, Corbin Bernsen, Henry Gibson, and Glenn Morshower. Collins most recently appeared in the acclaimed 2006 thriller Blood Diamond and had a major supporting role in the 2007 romantic comedy Because I Said So.
He had an Emmy-nominated role in the 1987 made-for-TV movie The Two Mrs. Grenvilles, co-starring Alan Oppenheimer and John Rubinstein. Other TV movies in which he starred include The Henderson Monster (1980, with Nehemiah Persoff), Sherlock Holmes (1981, with Frank Langella and Dwight Schultz), A Woman Scorned: The Betty Broderick Story (1992, with Thomas Kopache, Stephen Root, and Susanna Thompson), Remember (1993, with Gail Strickland), and On Seventh Avenue (1996, with Anthony Zerbe and Josh Pais). He has also co-starred with fellow Trek performers on a number of TV miniseries: 1977's The Rhinemann Exchange with Rene Auberjonois and John Hoyt; 1982's The Blue and the Gray, with Paul Winfield, Gregg Henry, William Lucking, Charles Napier, Duncan Regehr, and Noble Willingham; 1983's Chiefs, with Paul Sorvino and Leon Rippy; 1991's A Woman Named Jackie, with Bob Gunton and Tim Ransom; and 1994's Scarlett, with Colm Meaney and Paul Winfield. Recently, Collins has appeared in a reccurring role as Bruce in It's Always Sunny in Philadelphia (2006) and as Dr. Dayton King in the science fiction drama series No Ordinary Family (2010-2011, with Jimmy Bennett, Autumn Reeser, and Reggie Lee).
One of his more recent television appearances has been as a doctor in the series Revolution, co-starring Steven Culp. Collins' most recent lead role was as philandering murderous millionaire Phillipe Delatour on the Lifetime drama series Devious Maids co-starring Brett Cullen.
On October 8, 2014, a recording was released in which Collins confesses to his wife that he molested several underage girls prior to 2012.  Following the audio's release, Collins was fired from production on Seth MacFarlane's Ted 2.  The Christian cable network Up responded to the scandal by pulling 7th Heaven from air. Reports that the actor had shot and killed himself later that night proved to be false.  In December 2014, he admitted that the allegations of sexual abuse were true.