The NBC people, with ground to make up in the chase for television sports dollars, took a big bet yesterday on horse racing's never-before-staged Breeders' Cup Series, a seven-race extravaganza at Hollywood Park. The result: a big payoff for the network.

NBC's maiden plunge into important racing involved a $750,000 purchase of the rights to a program offering $10 million in purses, a sum that might be considered a vulgarity compared with the $7,900 Man O' War earned for winning the Belmont Stakes in 1921.

The gamble paid off handsomely for NBC, for the viewers at large and for the racing industry that has been trying to recapture lagging interest. NBC could, indeed, be peacock-proud.

At no time was there a sense that the four-hour exposure to horses and riders at work was inducing any chafing at what might have been an overextension of the plot. Happily for NBC and everybody else, each race told a different story and was steeped in excitement. It was far from your ordinary day at the races, the money aside.

Hollywood, appropriately, was the scene of all the goings-on, with unlikely scripts the norm for the day. As early as the second race, NBC was given an upset, with the $47 shot, Outstandingly, the winner following a long discussion by the stewards of a foul claim, Hollywood style.

For this day, the network made its own superb effort, with Pete Axthelm and Harvey Pack providing spice with irreverence in each prerace commentary, and not too shy to tell everybody who and why they liked a certain horse in each race. Axthelm hit the day running with his pick of that $47 shot in Race Two.

Everybody on the show was going public with his selections, including co-host Dave Johnson and the two Irishmen, Brough Scott and Michael O'Hehir, smartly imported for background on the foreign horses that were running. A regular passel of Jimmy The Greeks telling it like they thought it would be in each race. It didn't hurt.

If it wasn't quite a seven-game World Series, Super Bowl and Wimbledon rolled into one, as an overenthusiastic member of the cast proclaimed it, it was probably on an acceptable par with Derby Day, or one of the better Preakness or Belmont days. History was being made.

And in money terms, it was better than anything that's come before in the sport. For example, a fourth-place finish for Track Barron in the Breeders' Cup Classic earned his owner $210,000. For winning that one, Wild Again brought home $1,350,000.

There were the obligatory shots of Hollywood folks, the staple for all networks -- Cary Grant, Frank Sinatra, Linda Evans, Jack Klugman, Larry Hagman. Also Elizabeth Taylor, who, unfortunately, was asked for her selection in the fifth race. This veteran of seven marriages picked another loser, Life's Magic.

The racing was not only for degenerates. Everybody could thrill to the stretch duel that got the favorite Eillo home by a nose in the third race and to the game finish of Royal Heroine, the only lady in the 10-horse fourth race, who came from last to first.

NBC couldn't have written a better script for the Turf Handicap if it had tried. Fie on the favorites, All Along, the European; and Strawberry Road II, the highly rated horse from Australia, and Majesty's Prince. For a fact, the race was theirs with the finish in sight, but whoosh! Here comes Lashkari, the 53-to-1 outsider who seemed to be saying the race was his. It was.

The day built to a $3 million crescendo for the seventh race, the Breeders' Classic for 3-year-olds and up at a mile and a quarter. Could NBC and the Breeder People get lucky again in the big race? They could, in spades.

It was something. The 4-to-5 favorite, Slew o' Gold, didn't win it. Nor could Gate Dancer, the second choice, nor Desert Wine nor Precisionist. None of those. The envelope, please. And the winner is: Wild Again, at 25 to 1.

But the big race wasn't over when it was over. For NBC -- how lucky can you get -- more drama. Up went the "inquiry" sign, and the stewards were looking hard at all that bumping in the late stretch among Wild Again, on the rail, Slew o' Gold, in the middle, and Gate Dancer, on the outside. Any of those numbers could come down, maybe two. How sad for the long shot, who had hung on to win the nose-neck finish as bravely as you'd want to see. He was a game one, this Wild Again. But now . . .

Then, in the best tradition of Hollywood scripting, they gave it to Wild Again. They left his victory untouched. What's more, NBC could show a replay of Wild Again's owner telling an interviewer before the race, "We lost to Slew o' Gold in the east. I'm only waiting to get him on a California track."

Never did a network stike it so rich in such a sustained fashion. There wasn't a yawner on the whole program. The future of the Breeders' Cup Series is pretty clear now. NBC has a five-year option.