The principal action on the opening day of the Laurel Race Course meeting yesterday wasn't on the track.

It was in the stands, where Laurel was selling the new-style program containing past performances that offered direct competition with the Daily Racing Form.

Both the track management and the publication Sports Eye, which provides the past performances, worried that the reading habits of horseplayers would be difficult to change.

But by midafternoon their fears were allayed. The opening-day crowd of 7,899 bought 3,402 copies of the $1 program, compared with 2,708 copies of the traditional 50-cent program.

Sales of the Racing Form were cut sharply. Those figures could send reverberations throughout the industry.

Laurel's plan to publish a harness-type program had received not only the predictable opposition of the Daily Racing Form, but also objections from the Maryland Racing Commission, which required the track to keep selling a normal 50-cent program.

The track's response to this mandate was a sly one. It simply took the $1 program and removed all the past-performance data from it, leaving for 50 cents only the bare-bones information and a lot of white space in an unwieldly format.

The program even omitted the name of one of the entrants in the third race. Clearly, the intent was to motivate people to buy the $1 program. And it worked.

The new format elicited a wide variety of responses. One Sports Eye representative said the most common complaint he heard was that the jockeys' names were printed too small.

Some people found the program physically hard to manage, when they were hurriedly jotting down probable exacta prices or notes on the running of races. But ultimately the new venture will succeed or fail according to the quality of its past performances.

And they're not bad. The format is so similar to the Racing Form's that readers had little difficulty making the adjustment.

The most obvious shortcoming is the lack of any workout information, which can be especially important at the start of a season.

When Shadowfax came back from a five-month layoff to win yesterday's seventh race at long odds, readers of the program had no idea that he had recently recorded two swift workouts at Timonium.

The new program doesn't include the horses' lifetime records or their records for 1982. It apologized to readers that "certain breeding information" was not available but, for the casual fan, the past performances are more than adequate.

A serious horseplayer, of course, cannot live without the Racing Form. Not only does it provide far more extensive information, but it is available in an advance edition while the program is not.

Nobody who considers himself a serious player would wait until he gets to the track to begin his handicapping.

The initial success of its new program was just part of a happy day for Laurel, which was opening its season on an unusually early date. The season used to start in October, continue through the end of December and usually run out of steam along the way, a victim of bad weather and a general letdown that followed the Washington D.C. International.

This year's meeting runs through Dec. 11. Track President John Schapiro worried that the early dates might not succeed, that local racing fans would not be accustomed to going to Laurel when the trees are still green.

But yesterday's crowd and the handle of $1,032,081 were a marked improvement over its comparable opening day in 1981. Obviously the habits of horseplayers are a lot more malleable than anybody would have thought.