WASHINGTON (AP) _ The Marines who participated in the 1983 invasion of Grenada had to overcome a lack of intelligence information, poor maps and sporadic radio links to perform their mission, according to a new study released Tuesday.

The problems contributed to difficulties in quickly locating all the Americans on the island and at one point, almost led to the shelling of a building that housed the Venezuelan Embassy, the study said.

The ''operational overview'' of the Grenada invasion, written by the Marine Corps Development and Educational Command, was released at the Pentagon following a published report in The Washington Post. The newspaper said it had acquired a copy under the Freedom of Information Act.

The report is similar in some respects to a heavily censored ''Lessons Learned'' analysis released last month by Adm. Wesley L. McDonald, the commander-in-chief of the Atlantic Command. But unlike McDonald's report, which contained classified recommendations to the Joint Chiefs of Staff, the new report was written simply to describe the problems encountered by Marines.

It does buttress one key finding by McDonald, however, involving the use of helicopters. The report notes that even the least developed countries are now capable of obtaining weapons that can down helicopters and thus consideration must be given to attacking enemy anti-aircraft batteries before copters deploy.

''Numerous helicopters were lost to ground fire during the course of this operation,'' the Marine Corps report stated. ''Fortunately, no surface-to-air missiles such as the SA-7 Grail were located on the island, because this would have complicated matters greatly.''

The new report notes the 22nd Marine Amphibious Unit had been specially trained for duty in Lebanon and was already at sea on the way to the Mideast when the orders came to divert to Grenada. The review further suggests that American casualties could have been much greater than the 19 who were killed had it not been for the resourcefulness of ground commanders.

''The commanders on the scene had to make last-minute decisions,'' Pentagon spokesman Michael I. Burch said Tuesday of the report. ''But I think that's been the role of military commanders throughout history. You can never plan for all contingencies.''

Among the problems cited in the report that prompted improvisation on the ground:

-Few maps of the island were available and those that were tended to be outdated. That resulted in helicopter pilots being unable to land Marines at the locations originally specified.

-Communication problems were experienced throughout the Grenada action. ''The (battalion) commander (on shore) was restricted in the command and control of his remaining unlanded assets because he was not able to maintain adequate communications with them.''

-It was not until late in the day of the invasion that military commanders learned there was a second college campus on which students were barricaded. It took another day before Marines and Army Rangers were able to fight their way to the second campus and evacuate the Americans.

-A lack of solid intelligence also almost led to the shelling of an embassy. ''Because there was a flag of unknown type flying over the Fort Adolphus compound, the company commander considered using preparation fires to soften what he believed to be a possible Cuban stronghold. This consideration was reversed and prep fires were not used. This decision ... was sound, because as it turned out, Fort Adolphus was the Venezuelan Embassy.''

The Marine Corps report concluded with several ''discussion points,'' noting the defensive efforts by Cuban forces on Grenada offered little insight into ''Cuban tactics ... (because) the Cuban commander just did not have the time to do any better before the arrival of U.S. forces.''

''All the evidence indicates that, given more time, the enemy would have been much better prepared,'' the report said.