[2][3] Lansing is probably best remembered as the authoritarian Brigadier General Frank Savage in 12 O'Clock High (1964), the television drama series about American bomber pilots during World War II.

Lansing first appeared on Broadway in the play Stalag 17 (1951) directed by José Ferrer, replacing Mark Roberts in the role of Dunbar at the 48th Street Theater.

New York Times critic Clive Barnes praised Lansing's "mannered, tortured, and racked portrait of the Captain" as "superlative," comparing it favorably with a Michael Redgrave performance years earlier.

[11] Lansing appeared in Tennessee Williams' Suddenly, Last Summer and Eugene O'Neill's The Great God Brown in the title role.

His other stage performances included roles in Charley's Aunt, Elmer Rice's Cue for Passion, The Lovers, and The Cut of the Axe.

[4][12] Off-Broadway, his work included The Father, the "Sea Plays" of Eugene O'Neill, and two one-man shows, Damien and The Disciple of Discontent.

He guest-starred in two other episodes of the NBC's Western series: "Danger Road" (1970) as Gunny O'Riley and "Heritage of Anger" (1972) as John Dundee.

Robert Lansing is probably best known for his role as Brigadier General Frank Savage in the first season of the Quinn Martin production, 12 O'Clock High, which aired on the ABC Television Network from 1964 to 1967.

His other television roles include portrayals of an alcoholic college professor in ABC's drama Channing, as Gil Green in the 1963 episode "Fear Begins at Forty" on the NBC medical drama The Eleventh Hour, as a bounty hunter on Gunsmoke, and as a parole officer in a 1968 episode ("A Time to Love — A Time to Cry") of The Mod Squad.

He was the interstellar secret agent Gary Seven in a Star Trek episode ("Assignment: Earth", 1968), which also featured Teri Garr, and was originally intended as a backdoor pilot for an unsold new series.

Lansing's final television role was that of Police Captain Paul Blaisdell on the series Kung Fu: The Legend Continues.