He also spent a summer studying at the École des Beaux-Arts before earning a master's degree in Architecture from the Massachusetts Institute of Technology.

His early credits as art director included Charley's American Aunt (1941), and Belle Starr (1941), and he and Day won an Oscar for their work on Valley.

[4] Juran also worked on I Wake Up Screaming (1941), A Gentleman at Heart (1942), Ten Gentlemen from West Point (1942), The Loves of Edgar Allan Poe (1942), Dr. Renault's Secret (1942), It's Everybody's War (1942, a short), and That Other Woman (1942).

Juran enlisted in the Navy during the Second World War in July 1942 and was assigned to first the Office of Strategic Services and then to the Royal Air Force Intelligence Center.

Juran then signed a long-term contract with Universal, where he was the art director on Free for All (1949), Undertow (1949), Winchester '73 (1950), Deported (1950), Harvey (1950), Bright Victory (1951), Thunder on the Hill (1951), Reunion in Reno (1951), Cave of Outlaws (1951), The Strange Door (1951), Meet Danny Wilson (1951), Bend of the River (1952) and Untamed Frontier (1952).

[3] Juran was assigned as art department head for The Black Castle (1952), when director Joseph Pevney dropped out shortly before filming.

Juran returned to Hollywood to direct an independent film, Highway Dragnet (1954) based on a story by Roger Corman.

[7] Juran directed episodes of Fury (1954), Crossroads and My Friend Flicka on TV, and The Crooked Web (1955) for Sam Katzman at Columbia.

Instead of continuing with A features, he accepted two jobs "for the money", in his own words:[9] The Brain from Planet Arous (1957) then Attack of the 50 Foot Woman (1957).

Juran did a Western for Schneer, Good Day for a Hanging (1958) and, for TV, episodes of Frances Langford Presents, World of Giants, and Men Into Space (1960).

Schneer hired Juran to direct Siege of the Saxons (1963) and First Men in the Moon (1964) (based on the novel by H. G. Wells with effects by Harryhausen).