When baseball commissioner Bowie Kuhn takes the stand Tuesday in a suit brought against him by Charles O. Finley, much of the groundwork in his defense will have been laid by witnesses called by Finley.

Attorneys for Finley, irascible owner of the Oakland A's, have relied upon testimony from about a dozen witnesses to underscore their contention that Kuhn exceeded his authority in nullifying Finley's attempted sale of three Oakland players for $3.5 million last summer.

But the heavy-hitters on Finley's witness list have, under cross-examination by Kuhn's attorneys, been more helpful to the commissioner than to Finley.

In part, this may be because of Frank J! McGarr, the no-nonsense judge presiding over the case. He has said repeatly that the principal issues in the trial are whether Kuhn had the authority to veto the sales and whether he acted in good faith.

McGarr has rejected attempts by both sides to introduce testimony showing alleged malice on the part of Finley and Kuhn. The judge said that was irrelevant.

Neil Papiano, Finley's Los Angeles lawyer, has called a number of witnesses who testified that they believe Kuhn did not have the power to cancel the sales and that his authority was limited to areas involving gambling, moral turpitude, etc.

Among them have been Gabe Paul, president of the New York Yankees, who had agreed to buy pitcher Vida Blue for $1.5 million. Jeroid C. Hoffberger, board chairman of the Baltimore Orioles, in a deposition, agreed with Paul that Kuhn exceeded his authority in canceling the sale.

Papiano also called Lee S. MacPhail, president of the American League, who said he advised Kuhn to approve the transactions because no rules were broken and because he feared nullification would hamper negotiations then underway with the player' union.

In a deposition, Charles S. (Chub) Feeney, president of the National League, said he advised Kuhn against unsetting the sales.

But under cross-examination by Kuhn's attorney - Peter K. Bleakley, Irvin B. Nathan and Paul S. Reichler - the two league presidents said Kuhn had the absolute authority to void the sales and that he did so in good faith.

Dick O'Connell, general manager of the Boston Red Sox, who were supposed to obtain Rollie Fingers and Joe Rudi for $1 million each, said much the same in a deposition.

There also was testimony from former commissioners Happy Chandler and the late Ford Frick. Frick's views, excerpted from a congressional hearing, were stricken from the record because he could'n be cross-examined.

Chandler said, in a deposition, that Kuhn had the authority to veto the sales; Frick said he did not. But, Bleakley pointed out, Frick was commissioner during a period the office had been stripped of its powers.

When Frick left office, he recommended that the commissioner's powers be restored because his ability to function had been severely impaired. Furthermore, Frick recommended language that would allow the commissioner to exercise broad authority "in the best interest of baseball," the catch-phrase that is at the heart of the argument over Kuhn's authority.

There was also testimony from acquaintances of the first commissioner, Judge Kensesaw Mountain Landis, who attested to the post's broad, sweeping powers.

They also said the commissioner's job had been proposed before the Black Sox scandal in 1919 because the then-ruling body, a three-man commission, had the game in chaos because of their bickering.

Bleakley said he plans to call members of the executive council - John Fetzer of the Detroit Tigers, Ed Fitzgerald of the Milwaukee Brewers, John McHale of the Montreal Expos and Walter O'Malley of the Los Angeles Dodgers - before Kuhn. The trial is expected to end by Friday.