Born in Etobicoke, he is the son of Canadian television personality Elwy Yost, the longtime host of the public broadcaster TV Ontario's Saturday Night at the Movies. He lives in California with his family.
He has written extensively for television series beginning with the series Hey Dude in 1989. He was also an Executive Script Consultant for Hey Dude. He wrote the first season episodes "The Competition", "Perfect Father", and "Ted & Brad Get Handcuffed". He returned as a writer for the second season later in 1989 and scripted the episodes "Ghost Stories" and "Crash Landing". He remained a writer for the third season in 1990. He wrote the episodes "Inmates Run the Asylum", "Superstition", and "The Bad Seed". He remained a writer for the fourth season later in 1990 and scripted the episodes "Fear", "Return of Ted", and "Mr. Moneybags".
He became a writer for Herman's Head in 1991, scripting the first season episode "The Last Boy Scout". He then worked on the series The Powers That Be. He wrote the first season episodes "Bill Gets Shot" and "Kiss Me Caitlyn" in 1992. He returned as a writer for the second season in fall 1992 and wrote the episodes "Sophie's Big Decision", "Grandma's Big Decision", and "Having a Ball".
He wrote the action film Speed (1994). The film starred Keanu Reeves and Sandra Bullock and was directed by Jan de Bont. It was a box office success and Yost was nominated for an Edgar Award for Best Motion Picture.
He then wrote the action film Broken Arrow (1996). The film starred John Travolta and Christian Slater and was directed by John Woo. It was a moderate financial success. He also wrote the thriller Hard Rain (1998) which starred Slater and Morgan Freeman and was directed by Mikael Salomon.
He collaborated with HBO, Steven Spielberg and Tom Hanks on the production of the miniseries From the Earth to the Moon in 1998. He was a Supervising Producer and writer for the series. He wrote the episodes "Apollo One" and "Mare Tranquilitatis". He also made his directing debut on the series, helming the episode "Spider". Yost and the producers won the Emmy Award for Outstanding Miniseries in 1998. He was also nominated for the Emmy for Outstanding Writing for a Miniseries and the Writers Guild of America (WGA) Award for Episodic Drama for "Apollo One". The producers also won the Producers Guild of America (PGA) Award for Television Producer of the Year in Longform for the show. Yost wrote the similar Challenger film in 2000.
He wrote a draft of the science fiction film Mission to Mars (2000). He was credited as co-writing the screenplay for the film with Jim Thomas & John Thomas. The film starred Gary Sinise and was directed by Brian De Palma. It was a financial failure.
Yost collaborated with Spielberg, Hanks, and HBO again on the World War II miniseries Band of Brothers in 2001. He co-wrote the episode "Replacements" with Bruce McKenna and wrote the episode "The Breaking Point". The miniseries was a huge success and won multiple Emmy Awards. Yost and the producers were nominated for the Emmy Award for Outstanding Miniseries, Movie or Special for the show.
He wrote a draft of the screenplay for the film Last Castle (2001). The story and earlier drafts were written by David Scarpa. The prison drama starred Robert Redford and James Gandolfini and directed by Rod Lurie. The film received mixed reviews and was a financial failure.
In 2002 he co-wrote the television feature Young Arthur with Remi Aubuchon. The film was directed by Mikael Salomon and aired on the National Broadcasting Corporation (NBC) network.
He was the creator and head writer of the crime drama series Boomtown in the 2002 to 2003 television season. He was credited as an Executive Producer for the show. He wrote the series pilot and the later episodes "Possession", "All Hallow's Eve", and "Sinaloa Cowboys". He co-wrote the story for the episode "Fearless" with one of the series lead actors Mykelti Williamson. Yost wrote the teleplay for "Fearless". He won a Humanitas Prize in 2003 for the episode "Fearless". The series was renewed for a second season which began in fall 2003. Yost remained an Executive Producer and the series show runner and wrote the season premiere "The Love of Money". The series was canceled while airing its second season.
He wrote an episode of new family drama Summerland in 2004, entitled "Skipping School".
In 2006 he Executive Produced and co-wrote (with Chris Brancato) the television feature Sixty Minute Man. The feature was a bout a suburban father who realized that he had serial memory loss for an hour of each day and suspected that he was involved in a government conspiracy.
He was the creator of the short-lived NBC drama Raines starring Jeff Goldblum in 2007. He served as the Executive Producer and show runner for the series.
In 2008 he was a Consulting Producer for the HBO historical miniseries John Adams. The show was a critical success and won multiple Emmy Awards. He then re-teamed with HBO, Tom Hanks and Steven Spielberg to write, produce and direct episodes of the HBO miniseries The Pacific. He was a Co-Executive Producer for the project. He brought the Boomtown writers Michelle Ashford and Larry Andries on to the project. The project followed-up Band of Brothers by examining World War II in the pacific theatre. He co-wrote the episode "Gloucester/Pavuvu/Banika" with Robert Schenkkan. He also directed the episode. The miniseries went through a long post production process and aired in 2010. Yost and the production team won the Emmy Award for Outstanding Miniseries for the show. The producers also won the PGA Award for Television Producer of the Year.
In 2010 Yost developed Justified using Elmore Leonard's short story "Fire in the Hole" and the Raylan Givens character. Yost is a longtime fan of Leonard's writing. He is the head writer, show runner and an executive producer for the series. Justified premiered on FX in March 2010. It was renewed for a second season which aired in 2011. The writing stafff of Justified were nominated for the WGA Award for Best New Drama for the series in 2011.
During Falling SkiesEdit
He joined the crew of Falling Skies as a writer and Executive Producer for the first season in 2011. He wrote the series second episode "The Armory". His frequent collaborator Fred Golan also wrote for the show, scripting the third episode "Prisoner of War". Yost left the crew at the close of the first season.
He returned to Justified as the show runner for the third season in 2012.