Longing to be an actor since the age of five, Lamas first studied acting in Tony Barr's Film Actors Workshop and quickly thereafter obtained his first TV acting role in 1976. He had a supporting role in the 1978 film Grease. Early in his career, he also had guest-starring parts in Switch, Sword of Justice, Dear Detective, Secrets of Midland Heights, Fantasy Island, The Love Boat and Hotel.
In 1980, he auditioned for and won the role of Jane Wyman's playboy grandson and henchman, Lance Cumson, for the pilot of a new series entitled The Vintage Years. The pilot was later retooled to become the hit prime time drama series Falcon Crest. During a 2006 TV interview with Norwegian Television Team, Lamas said that to get the role on Falcon Crest, he had auditioned twice and beat out five other guys for the part. During his stint on Falcon Crest, Lamas was nominated for two Soap Opera Digest Awards and a Golden Globe Award. Lamas was the only actor to appear in all 227 episodes of the series.
In 1984, Lamas was nominated for Worst Actor at the Golden Raspberry Awards for his performance in the film Body Rock. Lamas also performed a song on the soundtrack for this film, and the track "Fools Like Me" became his only single to date to crack the Billboard Hot 100 chart.
In 1992, Lamas played the role of the falsely accused cop Reno Raines in the syndicated series Renegade. The series was seen in over 100 countries, and during its final season, it moved from first-run syndication to the USA Network. The show ended in 1997 after a run of five seasons.
From February 2004 until February 2007 Lamas played the role of Hector Ramirez on the CBS daytime soap opera The Bold and the Beautiful.
In August 2007, Lamas starred as the King of Siam in The King and I at the Ogunquit Playhouse in Ogunquit, Maine. That fall, he performed at Kean University Premiere Stages in Union, New Jersey in the title role in Steven Dietz's Dracula. Lamas performed as El Gallo in The Fantasticks at the Casa Mañana Theatre in Fort Worth, Texas in June 2008. In June 2009, Lamas returned to the Ogunquit Playhouse as Zach in A Chorus Line.
Lamas began appearing in the Zaxby's restaurant chain television advertisements in May 2008.
In 2008, Lamas appeared in season 2 of CMT's Gone Country.
In 2009, he starred in the Asylum's Mega Shark Versus Giant Octopus as Alan Baxter, a government agent who wants to destroy both the Mega Shark and the Giant Octopus to protect the world from their destructive fights.
In 2010, He starred as the voice of "Meap" in Disney Chanel's Phineas and Ferb.
Lamas is an avid Harley-Davidson motorcycle enthusiast, collects them and takes part in charity rides for a transplant fund.