Former White House aide Oliver L. North and his chief private collaborator in the Iran-contra operations, retired major general Richard V. Secord, shredded key documents relating to their activities within a day or two of each other last November, according to testimony released yesterday by congressional investigators.

The shredding of the governmental and private records was followed by meetings between the two men, attended by Washington attorney Thomas C. Green, on each of the four days beginning Sunday, Nov. 23. At the Nov. 24 meeting they were joined by Secord's business partner, Albert A. Hakim, who has so far refused to testify about the meeting but may be compelled to do so. On Nov. 25, Lt. Col. North was fired from the National Security Council staff.

In the period Nov. 21-25, Attorney General Edwin Meese III, on orders from President Reagan, conducted his review of the U.S.-Iran arms sales, discovered North's memorandum about a diversion of arms sales profits to the contras, and announced that there had been a diversion, that North had been fired and that his boss, national security adviser John M. Poindexter, had resigned.

The House and Senate select committees investigating the Iran-contra affair are focusing on this period to see whether key participants may have "manufactured their testimony" about key events "after the cover story was blown," a senior Senate member said yesterday. Independent counsel Lawrence E. Walsh is also looking into possible obstruction of justice and cover-up by participants.

In the testimony released yesterday, Secord's secretary, Shirley A. Napier, described her role in the fourth of those daily North-Secord meetings last Nov. 26. Napier said she delivered two boxes of phone, telex and other unshredded records from Secord's company to a suburban Virginia hotel where her boss, North and North's new attorney, Brendan Sullivan, were conferring. She said that she later put the boxes in Secord's dark blue 1984 Cadillac.

Secord testified to the select committees early last month that he had asked for the records in order to reconstruct financial data on his company, Stanford Technology Trading Group International. He testified that he took them home, looked through them and returned them to the office.

Napier told the committees that the boxes were not returned to Secord's Vienna, Va., office until March. The pertinent unshredded documents were subsequently turned over to Walsh's office, she said. Napier did not say who had the records in the interval, but they represented the only surviving documentation of Iran-contra activities in Secord's possession that could be turned over to investigators.

The material released yesterday provided new information about the actions of North, Secord, Green and Hakim during and after what Secord and Hakim have termed the "betrayal" of the private network by the Reagan administration.

Most important appeared to be a shift by Napier in her testimony about when documents were shredded at Secord's office. When first deposed April 10, and when testifying before Walsh's grand jury April 13, Napier recalled that the shredding took place in the first three weeks of December. She said that the delivery of documents to the Embassy Suites Hotel in Tyson's Corner occurred sometime thereafter.

But when confronted by the staff of the independent counsel with an American Express receipt for the hotel room dated Nov. 26, Napier revised her earlier testimony in a May 11 affidavit also released yesterday, and placed the shredding between Nov. 19 and 21. (Secord testified earlier that the shredding occurred in "early November.")

Last week North's secretary, Fawn Hall, testified that she had helped North shred a 1 1/2-foot-thick pile of documents at his Executive Office Building office on the afternoon of Nov. 21. The destroyed material, she said, included telephone messages, phone logs and other documents -- similar to the kind of papers that Napier said were destroyed at Secord's office.

Hall also testified last week that she had altered top secret NSC memoranda written by North in 1985.

Late Nov. 21, after the shredding, according to Hall, North met with Green away from his NSC office.

The next day, a Saturday, Justice Department officials reviewed North's files on the U.S.-Iran arms initiative and found an undated, five-page April memo from North proposing steps leading to a high-level U.S.-Iran meeting including the release of all U.S. hostages, the sale of 4,000 TOW antitank missiles to Iran and the use of $12 million in profits from the deal to "purchase critically needed supplies" for the Nicaraguan rebels.

On Sunday, Nov. 23, North went to the office of former national security adviser Robert C. McFarlane, where they discussed the diversion of arms-sales profits and the memo describing it, according to McFarlane's testimony. Secord and Green appeared and continued the discussion after McFarlane left them in his office, McFarlane testified. Soon after that, North went to the Justice Department office of Meese, where the attorney general and other officials questioned him.

On Monday, Nov. 24, North, Secord, Hakim and Green met at an undisclosed location. Hakim, citing the attorney-client privilege, has refused to say what was discussed. But later that day Green met with Assistant Attorney General William Bradford Reynolds to provide the government "certain information which it apparently did not then have," according to a summary of what Reynolds told congressional investigators.

Green, who said he had represented Secord and North in the past but was not calling on behalf of a client, told Reynolds that Hakim had been responsible for the diversion idea. According to the notes of the same meeting taken by Assistant Attorney General Charles Cooper, Green said Hakim had suggested to the Iranians in early 1986 that they could establish their "bona fides" by making a contribution to the contras or "to us," beyond the purchase price of the weapons. Green said this was the basis on which the United States sold weapons to Iran in 1986.

According to Cooper's notes, which the committees have released, Green said money from the arms sale was routed through the Israelis into Hakim's financial network. No laws were violated, Green told the Justice Department officials, because no U.S. money was involved and only Iranians were making a contribution.

This was essentially the position that Meese took at noon the following day, Tuesday, Nov. 25, when he held a news conference at the White House to announce the diversion, the firing of North and the resignation of then-Vice Adm. Poindexter.

That afternoon, North, Secord and Green met at the Embassy Row Hotel on Massachusetts Avenue. Later North and Green returned to the Executive Office Building and accompanied Hall when she smuggled classified NSC documents out of North's office.