(written from a Production point of view)
McNamara made his Hollywood acting debut in the 1984 film The Flamingo Kid, a movie which also featured fellow Star Trek performers Carole Davis, Googy Gress, and Steven Weber. This was followed with multiple appearances on the popular television series St. Elsewhere and High Street Blues, all occurring in 1986. During his time on St. Elsewhere, he worked alongside the likes of Chad Allen, Jeff Allin, Ed Begley, Jr., Norman Lloyd, Deborah May, France Nuyen, Jennifer Savidge, William Schallert, Alfre Woodard, and Jane Wyatt, while on Hill Street Blues, he appeared with James B. Sikking and Barbara Bosson. Also in 1986, McNamara was seen in a supporting role in the science fiction comedy Short Circuit, also featuring Barbara J. Tarbuck.
In 1988, he had a supporting role in the comedy Caddyshack II. The following year, he was seen opposite Star Trek: The Next Generation actress Denise Crosby and TNG guest actor Ed Lauter in the drama Tennessee Nights. TV credits during the 1980s included the movies On Fire (1987, with John de Lancie and Bill Erwin), The Betty Ford Story (1987, with Eric Menyuk, Sierra Pecheur, Kenneth Tigar, and Concetta Tomei), Earth Star Voyager (1988, co-starring Duncan Regehr), Police Story: Monster Manor (1988, with Erich Anderson, Lori Petty, Clayton Rohner, and Scott Burkholder) and guest appearances on Family Ties (on which he worked with Brian Bonsall and Meg Wyllie) and L.A. Law (starring Corbin Bernsen). In 1988, McNamara earned a Golden Globe nomination for his role in the previous year's telefilm, Billionaire Boys Club, which co-starred Raphael Sbarge and James Sloyan. And, in 1989, he, Molly Hagan, and Gregory Itzin were regulars on the short-lived sitcom The Nutt House.
After a supporting role in the popular film Arachnophobia (with Roy Brocksmith) in 1990, the majority of his credits during the 1990s are comprised of TV work. This include appearances on Murder, She Wrote (appearing along with Richard Beymer, Theodore Bikel, Len Cariou, Paul Carr, and William Windom), Murphy Brown, Seinfeld (with Jason Alexander and Richard Herd), Mad About You (in an episode also guest starring TNG star Gates McFadden), Sliders (with John Rhys-Davies), the new Fantasy Island (starring Malcolm McDowell and Mädchen Amick), and Touched by an Angel. He could also be seen in such TV movies as Perry Mason: The Case of the Heartbroken Bride (1992, with Ronny Cox, Paul Dooley, and Michael McGrady), and Without Warning (1994, with Ron Canada, John de Lancie, Marnie McPhail, and Alan Scarfe). He was also a regular on several short-lived programs, including Pig Sty (with Liz Vassey) and Mercy Point (with Larry Cedar and Jordan Lund).
He was more recently seen appearing with Vanessa Williams in the 2000 TV movie A Diva's Christmas Carol and with Marjean Holden in the 2001 science-fiction telefilm Code Red. He has also been seen on CSI, NYPD Blue, JAG (along with K Callan, Steven Culp, and Jennifer Savidge and series regular Scott Lawrence), and multiple episodes of The O.C.
He subsequently appeared in a family movie called The Tillamook Treasure, co-starring Brian Thompson (2006). He also directed and starred in a horror movie called Lost Signal.
Later, he starred as Major General Michael Holden on Lifetime's series, Army Wives.