TV series included Boomer and Miss 21st Century, Fantasy Island (several times), Faerie Tale Theatre, Tales of the Gold Monkey (a series regular), Small and Frye, Hotel, and George Burns Comedy Week.
Fox put him in another war movie, Confirm or Deny (1941), then he played Tyrone Power as a boy in Son of Fury: The Story of Benjamin Blake (1942).
Fox promoted McDowall to top billing for On the Sunny Side (1942). He was billed second to Monty Woolley in The Pied Piper (1942), playing a war orphan, then he had top billing again for an adaptation of My Friend Flicka (1942).
MGM borrowed McDowall for the star role in Lassie Come Home (1943), a film that introduced an Actress who would become another lifelong friend, Elizabeth Taylor. It was a huge box office success. That studio kept him on to play a leading role in The White Cliffs of Dover (1944), Peter Lawford as a young man, and another big hit.
Back at Fox he played Gregory Peck as a young man in The Keys of the Kingdom (1944). In 1944, exhibitors voted McDowall the number one "star of tomorrow".
McDowall turned to the theater, taking the title role of Young Woodley (1946) in a summer stock production in Westport, Connecticut in July 1946.
In 1947, he played Malcolm in Orson Welles's stage production of Macbeth in Salt Lake City, Utah, and played the same role in the actor-director's film version in 1948.
McDowall starred in seven films for them, for which he also worked as associate producer: Rocky (1948), a boy and dog story directed by Phil Karlson; Kidnapped (1948), an adaptation of the Robert Louis Stevenson story, where he played David Balfour, directed by william Beaudine; Tuna Clipper (1949), a fishing tale, again directed by Beaudine; Black Midnight (1949), a horse story directed by Budd Boetticher; Killer Shark (1950), a shark hunting tale, again with Boetticher; Big Timber (1950), as a logger; The Steel Fist (1952), an anti-communist drama.
His family moved to the United States in 1940 after the outbreak of World War II. McDowall became a naturalized United States citizen on 9 December 1949, and lived in the United States for the rest of his life.
He followed it with Escapade (1953) with Carroll Baker and Brian Aherne; Ira Levin's No Time for Sergeants (1955–57), which was a huge hit; Diary of a Scoundrel (1956); and Good as Gold (1957).
He had a big critical success with Compulsion (1957–58) based on Leopold and Loeb – although McDowall was not cast in the film version. He followed it with Handful of Fire (1958), Noel Coward's Look After Lulu (1959) and Peter Brook's The Fighting Cock (1960). The latter earned him a Tony Award.
He was Ariel in a TV production of The Tempest (1960) with Richard Burton and Maurice Evans, then appeared in his first Hollywood movie in almost a decade, The Subterraneans (1960). He followed it with Midnight Lace (1960).
McDowall continued to work on television in shows such as Sunday Showcase, Naked City, and Play of the Week. He was in a TV production of The Power and the Glory (1961) with Laurence Olivier, George C. Scott and Julie Harris.
McDowall was given his best film role in a long time, as Octavius in Cleopatra (1963). While filming in Europe, he appeared in Fox's blockbuster war movie The Longest Day (1963). He continued to guest on television series such as Arrest and Trial, The Alfred Hitchcock Hour, The Eleventh Hour, Kraft Suspense Theatre, Combat!, Ben Casey, Twelve O'Clock High, Run for Your Life, and The Invaders.
He had a support role in Fox's Shock Treatment (1964) and United Artists' The Greatest Story Ever Told (1965). He was third billed in The Third Day (1965) and one of many names in The Loved One (1965). McDowall went to Disney for That Darn Cat! (1965) and had a good part in Inside Daisy Clover (1965).
McDowall returned to leading man parts in films with Lord Love a Duck (1966) but the film was not a success. He appeared several times as The Bookworm on Batman and could be seen in The Defector (1966).
Disney gave him the star part in The Adventures of Bullwhip Griffin (1967) and he was top billed in The Cool Ones (1967) and It! (1967). He was in a TV production of Saint Joan (1967) and provided the voice for Cricket on the Hearth (1967). He guest-starred in The Felony Squad.
He published five books of photographs, each featuring photos and profile interviews of his Celebrity friends interviewing each other, such as Elizabeth Taylor, Judy Garland, Judy Holliday, Maureen O'Hara, Katharine Hepburn, Lauren Bacall, and others. It started with Double Exposure in 1968.
For the rest of the 1970s, McDowall alternated between features, TV films and TV series. Features included Funny Lady (1975), Mean Johnny Barrows (1976), Embryo (1976), Sixth and Main (1977),Laserblast (1978), Rabbit Test (1978), The Cat from Outer Space (1978) for Disney, Circle of Iron (1978), Nutcracker Fantasy (1979) (doing voice over for the English language edition), The Black Hole (1979) and Scavenger Hunt (1979).
As an actor he was in Pretty Maids All in a Row (1971). McDowall was not in the first Apes sequel but was in the second, Escape from the Planet of the Apes (1971). He was in the TV movies Terror in the Sky (1971), What's a Nice Girl Like You...? (1971) and A Taste of Evil (1971) and Disney's Bedknobs and Broomsticks (1971).
McDowall reprised his Apes part in Conquest of the Planet of the Apes (1972). He had support roles in The Life and Times of Judge Roy Bean (1972) and The Poseidon Adventure (1972) and starred in a pilot that did not go to series, Topper Returns (1973) and The Legend of Hell House (1973).
His final Apes movie was Battle for the Planet of the Apes (1973). He was in McMillan & Wife, Love, American Style, Arnold (1973), a remake of Miracle on 34th Street (1973), The Elevator (1974), and The Snoop Sisters.
In 1974, the FBI raided McDowall's home and seized his collection of films and television series in the course of an investigation into film piracy and copyright infringement. His collection consisted of 160 16-mm prints and more than 1,000 video cassettes, at a time before the era of commercial videotapes, when there was no legal aftermarket for films. McDowall had purchased Errol Flynn's home cinema films and transferred them all to tape for longer-lasting archival storage. No charges were filed.
Asked about his career in a 1975 interview, McDowall said "I just hope to keep working and in interesting things."
The TV movies included Flood! (1977), The Rhinemann Exchange (1978), The Immigrants (1978), and The Thief of Baghdad (1978).
McDowall's TV movie/mini series work in the 1980s included The Martian Chronicles (1980), The Memory of Eva Ryker (1980), The Return of the King (1980) (on which he did voice over work), The Million Dollar Face (1981), Judgement Day (1981), Twilight Theatre (1982), Mae West (1982), This Girl for Hire (1983), The Zany Adventures of Robin Hood (1984), London and Davis in New York (1984), Hollywood Wives (1985), and Alice in Wonderland (1985).
McDowall's features included Charlie Chan and the Curse of the Dragon Queen (1981), Evil Under the Sun (1982), Class of 1984 (1984), and Fright Night (1985), which became a cult classic.
McDowall began to play many voice over roles, such as Zoo Ship (1985), GoBots: Battle of the Rock Lords (1986), and The Wind in the Willows (1987). TV series included Bridges to Cross (1986) (in which McDowall was a regular), The Wizard, Murder, She Wrote, Matlock, and Nightmare Classics, and TV movies included Remo Williams: The Prophecy and Around the World in 80 Days (1989).
In 1987, he had supporting roles in Dead of Winter and Overboard, on which he also served as executive Producer. Other features included Doin' Time on Planet Earth (1988), Fright Night Part 2 (1989), The Big Picture (1989), Cutting Class (1989), and Heroes Stand Alone (1989).
In 1989 he said "I feel as Henry Fonda did that every job I get may be my last. I'm one of those creatures born to be working. I feel better when I'm working. I don't like it when I'm not working and I've never worked as much as I want to."
McDowall's 1990s work included The Color of Evening (1990), Shakma (1990), Going Under (1990), An Inconvenient Woman (1991), Earth Angel (1991), Deadly Game (1991), The Naked Target (1992), Double Trouble (1992), The New Lassie (1992), Quantum Leap, The Sands of Time (1992), The Evil Inside Me (1993), Dream On, Heads (1994), Hart to Hart: Home Is Where the Hart Is (1994), Mirror, Mirror 2: Raven Dance (1994), Burke's Law, Angel 4: Undercover (1994), The Alien Within (1995), The Grass Harp (1995), Last Summer in the Hamptons (1995), Bullet Hearts (1996), Star Hunter (1996), It's My Party (1996), Tracey Takes On..., Dead Man's Island, Remember WENN, Unlikely Angel (1996), The Second Jungle Book: Mowgli & Baloo (1997), Something to Believe In (1998), and Loss of Faith (1998).
He did voices for The Pirates of Dark Water (1991–92), Timmy's Gift: A Precious Moments Christmas (1992), Camp Candy, The Legend of Prince Valiant (1992), Darkwing Duck (1992), 2 Stupid Dogs, Swat Kats: The Radical Squadron, Batman: The Animated Series, Red Planet, The Tick, Galaxy Beat, Gargoyles, Duckman: Private Dick/Family Man, Pinky and the Brain, The New Batman Adventures, Superman, A Bug's Life (1998), and Godzilla: The Series.
In 1997, McDowall hosted the MGM Musicals Tribute at Carnegie Hall.
On 3 October 1998, at age 70, McDowall died of lung cancer at his home in Studio City. He was cremated and his ashes were scattered at sea on 7 October, off Los Angeles County. Dennis Osborne, a Screenwriter, had cared for the actor in his final months. The media quoted Osborne as having said, "It was very peaceful. It was just as he wanted it. It was exactly the way he planned."
McDowall served for several years in various capacities on the Board of Governors of the Academy of Motion Picture Arts and Sciences, the organisation that presents the Oscar Awards, and on the selection committee for the Kennedy Center Awards. He was Chairman of the Actors' Branch for five terms. He was elected President of the Academy Foundation in 1998, the year that he died. He worked tirelessly to support the Motion Pictures Retirement Home, where a rose garden named in his honour was officially dedicated on 9 October 2001 and remains a part of the campus.
Fox gave McDowall another starring vehicle, Thunderhead – Son of Flicka (1945). They reunited him with Woolley in Molly and Me (1945), an attempt to turn Gracie Fields into a Hollywood star.
