The Reagan administration was in a good mood at the Moroccan Embassy last night, chortling and chuckling its way through pigeon pie, the tax-bill victory, William Casey's survival and four courses that were followed by cigars.

"We're a very social administration," presidential counselor Edwin Meese remarked in what must be one of the grand understatements of 1981.

The party was given by Moroccan Ambassador Ali Bengelloun in honor of the Meeses, reason being that Ursula Meese is going to Morocco this month. That's as good an excuse as any for Bengelloun, the ambassador who doesn't like a week to slip by without a party.

His food and environs are always exotic. By mid-dinner last night, people at the round tables were wondering aloud if they'd have to be rolled to their limos.

"And we're only on the first course," East Wing staff director Peter McCoy joked as the third one arrived.

"That's how we count the missiles," observed Caspar Weinberger, the secretary of defense.

And when a waiter picked up the centerpiece of grapefruit at Meese's table, Meese blithely remarked: "Oh, there go the MX silos." A silo is a storage area in the ground that doesn't at all resemble a grapefruit, but everybody laughed anyway.

This particular party offered a large grab bag of administration significants:

Presidential secretary Helene von Damm, who had her own party Monday night and who's going with Meese to Morocco. Attorney General William French Smith, who went to von Damm's party. Bendix Corp. vice president and Reagan friend Nancy Reynolds, who's going to Morocco and who went to von Damm's party with ABC's Sam Donaldson. Weinberger, who's going to tonight's White House dinner for Anwar Sadat. White House aide Phyllis Kaminsky, who's going to Morocco with the other three. Commerce Secretary Malcolm Baldrige. And man-about-Washington Robert Keith Gray, who gives parties.

Contrary to popular lore, these people don't stand around at all these social events and make sweeping political decisions that affect lives and policy. At least they didn't last night. Table talk was as polite, jovial and innocuous as Sunday night at the country club, ranging from real estate and the lousy weather to August vacations and the Medfly.

"Jerry Brown has made the fruit fly what it is today," pronounced Meese.

There were 40 people in all, the bulk of them members of the Reagan in-group who've known each other for years. So it was relaxed and a lot less formal than the black-tie events that have become as common as Washington lunch plans.

"Oh, hi, Ed," the attorney general said to Meese as photographers pushed the two together, a standard practice that gets two presiding famous people in one frame. The attorney general smiled for the picture.

"The glass," said Meese, pointing to William French Smith's cocktail, which he held high in his hand.

"Oh, down below," said Smith as he moved his glass out of the camera's range. This is standard practice for those on the other side of the lens.

Smith and Meese were both fresh from maneuvers over the air traffic controllers' strike, but they kept their mouths shut.

"It's still going on," revealed Meese.

"We've taken the only course that could be taken under the circumstances," said Smith.

The four women -- Ursula Meese, von Damm, Reynolds and Kaminsky -- were much more talkative about their trip to Morocco. It's for five days, coming right after a 10-day political and social seminar they'll be attending in Egypt and Israel. They've also got an eight-hour stop in Paris.

"Starting with one afternoon in Paris," said von Damm, "we're going to go shopping, shopping, shopping."