James Norman Beaver Jr. was born in Laramie, Wyoming, to Dorothy Adell (née Crawford) and James Norman Beaver, a minister. His father's heritage was English and French. The family name was originally de Beauvoir.

Beaver graduated from Fort Worth Christian Academy in 1968 after transferring from Irving High School in his senior year. During high school, he showed interest in film history and writing, publishing short stories in the school anthology.

Fewer than two months after graduating high school, Beaver enlisted in the United States Marine Corps. He underwent basic training at Marine Corps Recruit Depot San Diego and trained as a microwave radio relay technician.

Beaver was transferred to the 1st Marine Division near Da Nang, South Vietnam, where he served as a radio operator and supply chief for the division communications company.

Beaver was discharged from active duty as a Corporal (E-4) and returned to the U.S. He remained active in the Marine Reserve until 1976.

After his release from active duty, Beaver returned to Irving and worked for Frito-Lay. He then enrolled at Oklahoma Christian University, where he developed an interest in theatre and debuted in The Miracle Worker.

Beaver made his professional stage debut in Rain at the Oklahoma Theatre Center in Oklahoma City.

Beaver's play, The Cop and the Anthem (adapted from the short story by O. Henry), was written.

Beaver and Debbie Young separated four months after marrying.

Beaver married Debbie Young, a fellow student, during his college years.

Beaver transferred to Central State University (now the University of Central Oklahoma) and performed in numerous plays. He supported himself through various jobs, including cab driving and working as a stuntman.

Beaver's play, Once Upon a Single Bound, was written.

Beaver's play, As You Like It, or Anything You Want To, Also Known as Rotterdam and Parmesan Are Dead, was written.

Beaver graduated with a degree in oral communications. During his college years, he began writing, completing several plays and his first book on John Garfield.

Beaver and Debbie Young officially divorced.

Beaver joined the Shakespeare Festival of Dallas, performing in numerous productions.

Beaver wrote the magazine article "John Wayne", which was published in Films in Review.

Beaver's first book, John Garfield: His Life and Films, was published.

Beaver's play, The Ox-Bow Incident (adapted from the novel by Walter Van Tilburg Clark), was written.

Beaver wrote the magazine article "George Raft", which was published in Films in Review.

Beaver was commissioned by Actors Theatre of Louisville to write the first of three plays for that company.

Beaver's play, Spades, was written.

Beaver moved to New York City, working onstage and writing plays while researching a biography of George Reeves.

Beaver wrote the magazine article "John Carradine", which was published in Films in Review.

Beaver wrote the magazine article "James Stewart", which was published in Films in Review.

Beaver's play, Sidekick, was written.

Beaver's short story, The Afternoon Blood Show, was published in Alfred Hitchcock's Mystery Magazine.

Beaver wrote the magazine article "Steve McQueen", which was published in Films in Review.

Beaver ghostwrote the book Movie Blockbusters for critic Steven Scheuer.

Beaver wrote the magazine article "Strother Martin", which was published in Films in Review.

Beaver moved to Los Angeles to continue research on his biography of George Reeves.

Beaver joined the Theatre West company in Hollywood as an actor and playwright.

Beaver's play, Semper Fi, was written.

Beaver's play, Verdigris, was produced to positive reviews, and he was signed by the Triad Artists agency.

Actress Maureen Stapleton played the leading role in a workshop of Beaver's play Verdigris at the Berkshire Theatre Festival.

Beaver's play, Verdigris, was written.

Beaver's play, Truth, Justice, and the Texican Way, was written.

Beaver received a CableACE Award nomination for his first TV script for Alfred Hitchcock Presents.

The Writers Guild of America strike fundamentally altered the freelance television writing market, halting Beaver's television writing career.

Beaver was cast in Norman Jewison's In Country, marking a turning point in his acting career.

Beaver married actress and casting director Cecily Adams.

Beaver's play, Pressing Engagements, was written.

Beaver starred in the television series Thunder Alley as Leland DuParte.

Beaver's daughter Madeline was born.

Beaver was cast as Whitney Ellsworth in the Western drama Deadwood.

Beaver's play, Mockingbird, was written.

Cecily Adams, Beaver's wife, died of lung cancer.

Beaver served as the historical and biographical consultant on the film Hollywoodland, about the death of George Reeves.

Beaver joined the cast of John from Cincinnati and played recurring roles on Supernatural and Big Love.

Beaver's play, Night Riders, was written.

Beaver's memoir, Life's That Way, was purchased by Putnam/Penguin publishers.

Beaver's memoir, Life's That Way, was published and chosen for the Barnes & Noble Discover Great New Writers program.

Beaver's performance in The Silence of Bees won him the Best Actor Award at the New York Film and Video Festival.

Beaver's play, The American Way, was written.

Beaver's play, Whigs, Pigs, and Greyhounds, was written.

Beaver was nominated for Best Guest Performance in a Drama by the Broadcast Television Journalists' Association Critics' Choice Awards for his role on Justified.

Beaver wrote and directed the short film Night Riders, based on his play of the same title.

Beaver's play, Lettering, was written.

Beaver was given the Lifetime Merit Award of the Idyllwild International Festival of Cinema.

Theatre West presented a 30th anniversary revival of Beaver's play Verdigris, with Beaver in a starring role.

Beaver began a relationship with actress and singer Sarah Spiegel.

Beaver returned to the Berkshire Theatre Festival to play Big Daddy in Tennessee Williams's Cat on a Hot Tin Roof.

Since 2018, Beaver has portrayed Secretary of Defense/U.S. presidential candidate/U.S. President Robert "Dakota Bob" Singer on the Amazon series The Boys.

Beaver and Sarah Spiegel were married.

Beaver filed for divorce from Sarah Spiegel, citing irreconcilable differences.

Beaver was awarded the 2023 Soaring Talent Award for Career Achievement by the Tallgrass Film Festival.

Beaver reprised his role as Bobby Singer in The Winchesters spinoff series.

Beaver's novella, Blood Show, a revision of the story The Afternoon Blood Show, was published by Nawyecka Productions.

Beaver's divorce from Sarah Spiegel was finalized.