A stern question mark hangs over the Iran-contra scandal: Why did it take the news media more than a year to pry the lid off this story? Earlier disclosure might have saved the United States from nasty embarrassment.

Until now, we have been restricted as to how much we could say about our role in the drama. We were sworn to protect sources who have now released us to tell the story. If in this recounting we give too much weight to our own part, it is because we know that part best.

Not long after the White House opened back channels to Iran, we heard about the covert negotiations. We asked President Reagan's national security adviser, Robert C. McFarlane, about the rumors in mid-November 1985. He was evasive.

We continued checking until we became convinced that significant negotiations were going on, that the administration was making deals in conflict with its policy toward terrorism.

Our inquiries precipitated an urgent call to Dale Van Atta from Noel Koch, then deputy assistant secretary of defense for international affairs. Testifying under oath 18 months later, Koch told Congress that Van Atta had the whole story in December 1985. "He had it cold," said Koch. "He came to me and asked me about it . . . . I simply said, 'Would you please drop it? I think if you go with this story . . . you may get somebody killed.' "

Rather than risk the hostages' lives, we sat on the story. But we were troubled by the administration's attempt to conceal its negotiations behind an elaborate smoke screen. The White House orchestrated a campaign to portray Reagan as the scourge of terrorists and Libya's Moammar Gadhafi as the terrorist most in need of scourging.

We knew the administration was offering arms to the most deadly terrorist of them all, Iran's Ayatollah Ruhollah Khomeini, and published columns protesting that Khomeini, not Gadhafi, was behind most terrorist acts against the United States.

As evidence, we reported on Dec. 13, 1985, the death by torture of hostage William Buckley, a high Central Intelligence Agency official. His capture and torture, we reported, were ordered by Tehran.

The day that the column appeared, McFarlane's administrative assistant, Karna Small Stringer, screamed at Van Atta on the telephone that we were putting all hostages at risk.

On Feb. 24, 1986, Van Atta reviewed our findings with Reagan in the Oval Office. He confirmed that Buckley had been tortured to death but that, to save the hostages, he was dealing with Khomeini's regime. The president urged us to withhold the story until the hostages were released.

On April 28, 1986, we reported cautiously that "the Reagan administration has begun a hush-hush, barely perceptible tilt toward Iran." We followed up with more details in May and June.

Yet the White House succeeded in keeping the press in a bottle. Reporters complained to us that they could not confirm our stories, bumping up against a stone wall at the White House.

In a Sept. 17, 1986, memo, an anguished Lt. Col. Oliver L. North speculated who might "be the source of the Jack Anderson stuff we have seen periodically." Still the conspiracy of silence held until last November.