Was it the first major film broadcast on network TV? No, NBC debuted MEET JOHN DOE back in 1950. MGM's first in-house film to hit the networks? Only if you ignore the three-part serializations of CAPTAINS COURAGEOUS and THE PIRATE on ABC's "MGM Parade'' earlier in 1956. #TCMParty 
Was OZ first feature broadcast in color on a network? No, NBC had colorcast THE CONSTANT HUSBAND in 1955 and Olivier's HENRY V in May 1956. OZ might have been the first US feature though, because ABC showed THE PIRATE in black and white, just as they did THE RED SHOES. #TCMParty
ABC also broadcast condensations of several Technicolor cartoon and live-action features in black and white on its "Disneyland'' series before the OZ debut, beginning with ALICE IN WONDERLAND (1951) on 11/3/54. #TCMParty
So a network showing a major Hollywood feature, uncut and in color, was a very big deal in 1956. A few days before the broadcast, CBS staged a photo op with Garland's daughters, Liza Minnelli and Lorna Luft, who watched the film on a monitor. #TCMParty
Many years later, Lorna Luft told me the sisters had never seen OZ before and they were terrified. Their mother was performing at RKO Palace on Broadway and made sure she was there the next time they saw it, Lorna said. #TCMParty
As CBS' first choice Garland was unavailable, the first telecast was hosted by her co-star Bert Lahr, with Minnelli and 10-year-old Justin Schiller as guests. All that's known to survive is a portion of the intro recorded on audio tape by a fan.
For all the attention the debut got, CBS didn't around to exercising first of options for 2 repeats until 12/13/59, when Red Skelton, with his daughter Valentina Marie, hosted what became the first of the (almost) annual broadcasts. This time it began at 6 instead of 9. #TCMParty
Skelton's segments were pre-taped, as were the ones that host Richard "Have Gun Will Travel" Boone and his son Peter shot on location in Apache Junction, AZ for CBS' third telecast on 11/13/60. #TCMParty
12/10/1961 at 6 pm. Fourth OZ telecast, the only one entirely in black and white after CBS' sponsors balked at a color surcharge. Hosted by Dick Van Dyke, joined by his children Christian, Barry and Stacey as well as the family dog Alice. #TCMParty
12/9/1962 from 6 to 8 pm on WCBS. OZ was broadcast only in color from this point on. The Van Dykes were back in a whole new intro that included a look at Dick's sketches of the film's characters for the fifth showing. #TCMParty
CBS did not show OZ in 1963. First of 4 post-holiday broadcasts, the sixth, on 1/26/64 with Danny Kaye introducing "from a leprechaun's perch atop gaily colored mushrooms,'' according to the Boston Globe. Kaye returned to host annual institution on CBS through 1967. #TCMParty
Saturday 4/20/68 at 7 pm. Though OZ got great ratings, CBS balked at MGM's rising licensing fees after nine showings. NBC leased it from 1968 through 1975, doing away with wraparounds due to the growing amount of commercial interruptions and moving it to spring. #TCMParty
Sunday 3/15/70 from 7 to 9 on NBC. Twelfth telecast opened with Gregory Peck reading a brief statement about Judy Garland, who had died the previous June. The donation was given by the Singer Corporation, which sponsored this year's telecast.
Sunday 3/14/76 at 7 pm. For 18th showing, OZ returned to CBS, where it aired every year (except 1992, 1995 and 1997) until 1998 with two showings in 1991 and 1993. Beginning in 1985, it was time compressed several times to avoid cuts as commercial loads increased. #TCMParty
Tuesday 2/20/90 from 8 to 10:15 pm. CBS marked 50th anniversary by showing OZ in longer time slot for the first time (no compression) with opening/end restored to sepia. Angela Lansbury hosted the film, followed by a 45-minute documentary produced by Jack Haley Jr. #TCMParty
Friday 5/8/98 at 8 pm. 39th legacy network broadcast was last for CBS, which had extended its OZ license in a deal that involved surrendering balance of its 20-year lease on GONE WITH THE WIND, which never lived up to the network's hopes as a perennial, to Ted Turner. #TCMParty
OZ hasn't been entirely a cable exclusive, though TCM, TNT and TBS have all shown it lots. According to the excellent Wikipedia page on OZ's TV history, it was also shown on sister company Warner's WB broadcast network annually from 2003 to 2005. #TCMParty
