The staff of Sen. David Boren (D-Okla.) had been waiting for the big event for a month. In what has become an annual ritual, legislative assistant David Cox counted off the days with a red magic marker on the office calendar. The summer interns could hardly wait.

At last came the day of the third annual "Ice Cream for America" party, sponsored by the International Association of Ice Cream Manufacturers. The promise of free ice cream drew members of Congress and their staffs by the thousands into the courtyard of the Russell Senate Office Building yesterday in search of the sweet confection.

Said Rep. Byron Dorgan (D-N.D.), "Every group that puts on events always has trouble getting Congress people. If any group is bound to be successful it's the one that offers ice cream." Lobbyists and party-givers, be advised.

"It's important to show the interns that ice cream is a pivotal part of the summer and the United States," said Cox, who takes his ice cream seriously. He "snarfed down" more than eight dishes. Asked how he could fit so much ice cream in, he disclosed his method: "You have to pace yourself." He also skipped dinner Wednesday night and lunch yesterday to save his appetite.

Bill Baar of Borden Milk, one of the more than 100 members of the ice cream association who attended the event, said it was no surprise to him the event drew more than 8,000 people. "Everybody wants to be identified with ice cream."

Sen. Robert Dole (R-Kan.) said politicians like ice cream because it's digestible, delicious and easy to swallow if you need to talk to someone after you've just taken a big mouthful. "It's a great political plus. I think I'll try to get the Senate to stop debating and start eating."

Other statements of devotion ranged from that of Sen. John Kerry (D-Mass.) -- "I eat ice cream almost every day" -- to that of hard-core aficionado Sen. John Danforth (R-Mo.) -- "I spend a great deal of my life eating ice cream or thinking about eating ice cream."

On a more serious note, Danforth said he felt that the Reagan administration was handling the Beirut hijacking appropriately. "I don't think we have any real options. I don't think we can make concessions or urge Israel to make concessions."

Rep. Patrick Swindall (R-Ga.) noted that government officials are consciously continuing with "business as usual" despite the hijacking of TWA Flight 847 to Beirut. "It's very important that when acts of terrorism occur, that they will not shut down our government."

The issue of how ice cream should be eaten provided some distracting, if small, controversy. Cox said the caramel toppings, crunchies and whipped cream were crucial to the true ice cream connoisseur.

Martha Redstrom-Plourd, personnel officer for the Senate computer center, shunned the toppings. "Just the pure ice cream," she said firmly, dipping into a bowl of pralines and cream.

Chris Tiernan, who works for Sen. Bill Bradley (D-N.J.), contended that the best way to eat ice cream was with one's tie tossed over one's shoulder, so that one may return -- stainless -- to work afterward.

One of Boren's interns, Shreese Stephenson of Watonga, Okla., was treated to a birthday serenade by the six-man band that played church-social-style music all afternoon under a red-and-white-striped canopy. Stephenson was 22, and didn't feel a day older. "I'm very happy," she said. "It's probably the highlight of my summer."

The only lukewarm response came from one of the youngest guests. Lulu Liao, 6, said she liked her vanilla ice cream just fine. But in the interest of accuracy she quickly amended herself: "Oh well, a little bit. Medium."