OBVIOUSLY IT depends on your perspective. To a Hill staffer, who may never eat at Lion d'Or, the annual "shellfish extravaganza" put on by the Shellfish Institute of North America is the "most coveted" lobbying party on the Hill.

To a rich, bored lobbyist, who drinks more than he eats, even a $12,000 bash "is still a two-bit party."

The staffer was only interested in the food; the lobbyist only in the people. Reminded that several representatives and senators had shown up, among them Sen. Strom Thurmond (R-S.C.), the lobbyist retorted: s"But Strom Thurmond is anywhere there's food."

But for those who are turned on by an oyster sampling, this extravaganza was the place to be. The raw bar featured Chincoteagues, New England, Long Island and Eastern Shore oysters. Right next to them were Little Neck and New England clams.

All the recipe preparations, by the way, were named for members of the House Committee on Merchant Marine and Fisheries, which explains why there was a dish called Oysters Rockefeller a la Breaux and a Chowder Murphy. The committee chariman, John Murphy (D-N.Y.), was also listed as host.

You could tell the old hands by the way they slurped the oysters right off the shell. Among them was Maryland Rep. Barbara Mikulski, even though she was worried that it would "drip down my dress, and I have to go out after."

For those who think eating a raw oyster is about as appetizing as eating a sheep's eye, there was plenty of cooked seafood. An estimated $2,000 worth of shrimp was down to the ice 30 minutes after the party started (and 1 1/2 hours before it was over). But there were plenty of baked oysters, pan-fried scallops, crab fingers, breaded something or other, probably crab, two kinds of clam chowder (neither authentic), cornbread, coleslaw, and fruit.

Unfortunately, when you use one of the rooms in the Rayburn Office Building for a party, you have to put up with their cooking. Doubtless all of the raw ingredients that went into the cooked dishes were superior, but we'll never know.

And obviously that's a hypercritical observation, at least as far as Mike Arnett was concerned. Noticing a reporter taking notes, he sidled up and said: "You want to talk to me."

"I do?" was the snappy comeback.

"Yes, because I've snuck in here for the fifth year in a row and I do it differently each time. I try to hit this one every year."

Arnett obviously wanted to tell how he got past the plainclothes security guards without the required card saying, "Admission by invitation only. Invitation not transferable. Redeem invitation for name badge at door."

"How?" he was asked.

"You can come in the side door when someone leaves with a tray. You can rush in as if you have an important document. You can go in through the committee office, which is the room next to this one. And one year, when it was held in the Longworth Cafeteria, I went in through the kitchen." Arnett used to work on the Hill. Right now he's between jobs . . . but eating well.

The people who run this party for 1,000 on behalf of the Shellfish Institute insist that it is not a lobbying event, that very little business is conducted, that it is very selective in its invitation list, that Hill staffers are not welcome in place of their bosses.

Fully half of the people had name tags that read "Cong. X's office."

"Then how come there were so many people from Congressman Mendell Davis' office, the PR man, Josh Lanier, was asked. "They just walked in with him," he said. "They learned the trick. He comes up and says: 'These are my staff.' What can I say?"

How about "Welcome."

Without the staffers the hall would have been only half full, and what fun is a Hill reception if hundreds of unknown people aren't jostling your drinks and elbowing you away from the buffet table.

A trio of cooking experts will join William Rice and Marian Burros at The Post's spring Book and Author Luncheon on April 25. The luncheon, at 12:30 in the Sheraton Hall of the Sheraton Washington Hotel (the renovated and renamed Sheraton Park), will feature a question and answer session with the editors and John Clancy, Judith Olney and Joan Nathan.

Clancy, the noted New York City teacher, is a specialist in baking and author of the recently published "John Clancy's Fish Cookery." Olney, who lives in North Carolina, has two books to her credit, the most recent being "Comforting Food." She has written or been written about in most leading magazines that feature food. Nathan, who contributes frequently to these pages, will speak about her book "The Jewish Holiday Kitchen."

Tickets for lunch plus the program are $10. They may be purchased at major bookstores in the District, Chevy Chase and the Virginia suburbs, at The Post's front counter, or by mail. Send a check payable to The Washington Post and a self-addressed, stamped envelope to Book and Author Luncheon, Public Relations Department, The Washington Post, 1150 15th St. NW, Washinton, D.C. 20071.

Other cookbook authors have been passing through town recently, notably Maurice Moore-Betty, who did the "Maurice Moore-Betty Cookbook" for Bobbs-Merrill ($14.95). From his classes and catering in New York City, he has come to the conclusion that "there's a revolution going on at the moment, a very good one. People have realized that food doesn't have to be French to be good.

"It is a very practical age. Entertaining with food can be very informal. Menus are better planned. I've found people are beginning to appreciate a great many foods that went out of style. I've had great success with recipes such as queen pudding (an almond-flavored Victorian dessert that utilizes custard and meringue), cottage pie, braised lamb shanks and floating island."

Moore-Betty does realize the value of a French name, however. He teaches his students a meatloaf recipe and tells them to call it pate chaude when they serve it to guests. "It's nonsense," he said, to say that some food 'is not good enough for company.' If it's good enough for you, it should be good enough for somebody else -- as long as its well cooked."

Helen Worth, who recently relinquished her title as the dean of New York City cooking teachers by marrying and moving from the city, was presiding at a banquet in her honor at the Golden Palace. The occasion was the reissue in hardback of her "Cooking Without Recipes" (Bobbs-Merrill, $10.95). While the book does contain a few conventional recipes, her object is to have readers absorb methods and techniques by learning what she calls "recipe patterns."

She and her husband plan to move soon to Charlottesville, where she may well continue her teaching.