Dickie Moore was in some early to late 50’s tv after his many movie roles.
Since someone just mentioned the guy in another thread, I can’t help but add that Angus Lennie of The Great Escape fame acted on Armchair Theatre in '57 and '58 before doing a TV movie in '59, after which he of course kept acting on television in the '60s and '70s and '80s and '90s and '00s.
Back before Liselotte Pulver spent the early 1960s acting alongside Jimmy Cagney in One, Two, Three and earning a Golden Globe nomination in a Bob Hope comedy, she was playing the titular role in a 1956 Joan of Arc TV movie – after acting in another TV movie, and another other TV movie, after her big-screen debut in 1950 with future television personalities ranging from Richard Erdman to Alan Hale Jr.
Mickey Kuhn, who was Beau Wilkes in Gone With The Wind long before appearing back alongside Vivienne Leigh in Streetcar Named Desire, acted in episode after episode after episode of Alfred Hitchcock Presents before the end of '57.
After big-screen westerns in the '40s, William Phipps made his television debut in '51 with Adventures of Wild Bill Hickok before acting on episodes of Annie Oakley and doing the Indian Agent TV movie before spending '56 and '57 and '58 and '59 and '60 and '61 playing Curly Bill Brocius on The Life And Legend Of Wyatt Earp.
I don’t need to tell you that he racked up plenty of other pre-'58 television credits on everything from Cheyenne to Wagon Train to Broken Arrow to Colt .45 to Trackdown to The Restless Gun to The Cisco Kid to The Adventures of Kit Carson. I will, though, add that after serving in WWII, he voiced Prince Charming in Cinderella.
After acting in dozens of movies during the 1930s and 1940s, Gene Reynolds acted on dozens of TV shows before the end of 1957: I Love Lucy, The Lone Ranger, Dragnet, you name it. He then spent the '60s and '70s earning dozens of Emmy nominations as a writer/director/producer, and then kept working in the '80s and '90s and '00s.
After making her movie debut in '47, Dolores Hart made her TV debut in '57: acting on Alfred Hitchcock Presents the same year she was appearing alongside Elvis Presley in Loving You. She kept at it in '58, acting on Matinee Theatre and Schlitz Playhouse easy as appearing alongside Elvis in King Creole. In '59, she was still acting on television easy as earning a Theatre World Award on Broadway. In '60, she was still acting on television and starring in Where The Boys Are. And after yet more work on television and in the movies, she’s now – Prioress of the Benedictine Abbey of Regina Laudis.
Recent subject of the Oscar-nominated documentary God Is The Bigger Elvis.
George Maharis picked up a number of TV acting credits before the end of '57, after which you could see him on The Phil Silvers Show in '58, and on Naked City episodes in '59, followed by his Emmy-nominated role on Route 66 from '60 to '63.
In '51 and '52 and '53, Mara Corday was acting on The Adventures of Kit Carson, after which you could see her on The Colgate Comedy Hour in '54, and The Bob Hope Show in '55, and Combat Sergeant in '56, and et cetera. And she kept at it after becoming a Playboy Playmate in '58, still acting on TV in '59 and into the '60s.
But never mind that now; instead, note that she was second-billed in Tarantula, the movie that’s maybe most famous for giving a small part to young Clint Eastwood; at that, look over her post-'60s credits: The Gauntlet in the '70s, and Sudden Impact in the '80s, and The Rookie in the '90s, and – look, the point is, if Mr. Eastwood is so much as making Pink Cadillac, there Ms. Corday will be.
After making her TV debut on The Mel Tormé Show, pretty perky Peggy King was featured on The George Gobel Show in 1954 and 1955 and 1956 before getting work on The Jonathan Winters Show and The Bob Hope Show and The Steve Allen Show and The Nat King Cole Show and et cetera before the end of 1957.
Was performing live in 2013, is set to appear in a documentary in 2015.
After making her big-screen debut with Bob Cummings in '53, Mary Costa made her small-screen debut in a TV movie of A Christmas Carol in '54, followed by – well, acting on The Bob Cummings Show in '55, followed by hosting episodes of Climax! before appearing on The Jack Benny Program in '57, followed by providing the voice of Princess Aurora in Sleeping Beauty in '59.
She kept at it in the '60s – singing on The Ed Sullivan Show, acting in a TV movie with Jeremy Brett, and so on – before earning a Golden Globe nomination in the '70s; she was a commencement speaker in 2012, she made a documentary appearance in 2013, and as far as I can tell she’s still alive and well here in 2014.
Michael Medwin did a TV movie in the '40s, acted on TV show after TV show after TV show before the end of '57, and spent the '60s and '70s and '80s on the big screen before returning to TV movies in the '90s – Alice Through The Looking Glass, with little Kate Beckinsale – and '00s – Cinderella, with big Kathleen Turner.
I see where nonagenarian actor Jack Carter has already been mentioned, but I don’t yet see his octogenarian ex-wife Paula Stewart making the list – but before she was acting on Perry Mason, or singing on The Ed Sullivan Show, or making the rounds on the Jack-Paar-era Tonight Show, or whatever, she was making her TV debut in '56.
(Alongside young Carol Burnett, as it happens.)
Since he’s being mentioned in another thread, I’ll note that long before WWII veteran Norman Lear hit it big with All In The Family and et cetera, he was busy writing and directing and producing The Martha Raye Show back in '54 and '55, and before that he was writing for – and occasionally appearing on – The Colgate Comedy Hour.
Any Irving’s mom – and thus, Steven Spielberg’s mother-in-law – Priscilla Pointer is still alive long after making her small-screen acting debut in '54, followed by showing up in everything from Adam-12 to Blue Velvet to Carrie to Dallas to ER to Family to Generation to Hemingway – with Stacy Keach as Ernest Hemingway! – and so on.
After doing movies with John Garfield and Tyrone Power and Errol Flynn in the early 1950s, Micheline Presle made her television debut on The Ed Sullivan Show in 1957 before doing more than half-a-dozen TV movies (and Combat!) in the 1960s; she was still at it in the 1980s – with Tales of the Unexpected and Ray Bradbury Theatre and et cetera – and was still acting as recently as last year.
Mary Healy appeared alongside her husband Peter Lind Hayes in Lux Video Theatre and Make Room For Daddy and The Ed Sullivan Show and Goodyear Playhouse and What’s My Line and Studio One In Hollywood and Perry Como’s Kraft Music Hall and The Jackie Gleason Show and Armstrong Circle Theatre and so on, all the way back to Inside USA With Chevrolet in the '40s – all well before (a) the deadline, after which they were of course (b) acting together on Peter Loves Mary in the '60s.
Back before Cliff Robertson was earning an Oscar for Charly, he was getting the hang of the role in “The Two Worlds Of Charlie Gordon” on The United States Steel Hour in '61 alongside veteran actor Gerald S. O’Loughlin, who’d racked up TV and movie credits prior to the OP’s cut-off date when he wasn’t busy acting on Broadway.
(Years later, O’Loughlin was still on Broadway: understudy in the role of McMurphy for One Flew Over The Cuckoo’s Nest, which was being played by Kirk Douglas, who’d bought the rights, which is how Michael Douglas came to get his first Oscar producing the movie version in the '70s; that’s, like, a matryoshka doll of Oscar trivia.)
Margaret Barton did half-a-dozen big-screen movies in the 1940s before switching to TV movie after TV movie after TV movie after TV movie before the end of '57.
The recent death of Richard Kiel got me looking at the IMDb entries of the great Twilight Zone episode “To Serve Man” and the actress therein Susan Cummings, who appears to still be alive. Her listed TV credits start in 1952, but along the way she also appeared in the movie Swamp Women!
Kiel’s acting career started in 1960, so he didn’t qualify for this thread. With his death, Cummings appears to be the last credited player from that episode still alive.