IF YOU DON'T count the Mitch Snyder fast, the only thing of consequence that has occurred in the capital this year is the opening of a McDonald's restaurant (specializing in beef patties garnished variously) right next to Sans Souci.

Sans Couci is a restaurant famous mainly because Art Buchwald, columnist, (and several generations of White House types) have fed there during waking hours and the world, therefore, keeps hearing about it.

Rumors instantly began to circulate:

The entire clientele of Sans Souci has moved next door.

McDonald's is in trouble because all that crowd has been seduced by the SS pumpkin timbale a la trolloppe .

Neither is true. Kay Goff, speaking for McDonald's corporate headquarters, stated that the new place is "doing real well" and even better than expected.

A lot of people near Pennsylvania and 17th St, NW have been looking for a place where you can dine in less than two hours for less than $24.99 and can persuade somebody that you really do want coffee with lunch.

So the place has been busy indeed, even at 2 p.m., when six of the eight checkout lines were operating the day I feasted there on pate de boeuf grille a la maniere de gross caledonie (Big Mac) with various additional side dishes to the total of $1.74.

An owner of Sans Souci, Bernie Gorland, said his business has not collapsed from the competition, however.

"It's pretty silly, I think, to compare Sans Sourci and McDonald's. You go there to eat, you come here to dine."

I did not think to ask Gorland how often he ate at Sans Souci, but I did ask him if McDonald's was behaving itself and being (within its limitations) a good neighbor.

"Yes. So far, a very good neighbor."

So far?

"I did see one box, the kind they put the Big Mac in, in the alley," he said.

Really. How quibbly can you get. I once slipped in front of Sans Souci on a Caened tripe, but never blamed Sans Souci for it.

"I sometimes eat at McDonald's myself," Gorland said, wondering if his crack about the Big Mac box was too elitist.

My own investigations show that two-thirds of the McDonald's customers (some of them reading ecology books and one studying the Sunningdale Nurseries catalogue) looked Sans Soucique and two-thirds of the Sans Souci crowd looked Big Macable.

There are 40 pots of tropical vines and ferns hanging all over McDonald's, and one is depressed at the thought of watering so many. Also there is no mustard available at McDonald's. You have to stand in line and say, "Hey, I need some mustard." (Corporate offices say they are entertaining this complaint, and mustard squirters may be installed. Catsup, they say, is already dispensed upstairs. As if that had anything to do with it.)

The grand eateries of the town may say what they like, but the future is obviously with McDonald's. Not because the general level of taste is so low (though it may be.)

But because so many of us have had it just about up to here with sloppy waiters and expensive food that obviously was shipped up by truck from the City Cafe of Pearly Bluff, Miss.

The man who adopts the McDonald's principles and turns out two or three good dishes (a beef stew for $2.10, a tuna quiche for $1.12 and a cup of drinkable coffee for a quarter) will make a fortune.

And some day it will be done. In the meantime, I found my first luncheon at Chez Mac a revelation. Eating out does not have to be a pain in the neck.

The next day I had lunch at the National Press Club where for $8 you can get one of the most memorably wretched lunches you ever ate. Fried macerated Beaverboard was the specialty of the day garni, with broccoli sweepings and Elmer's Gelatinous for dessert.

But then everybody's mind was on a higher plane -- it could hardly be on a lower -- since Billy Graham, the evangelist, was luncheon speaker. He said many fine things and is opposed, I felt, to the devil.

Religious speakers like Graham are valuable in a society. I remember at the time of the shocking Profumo scandal in England (English scandals are infrequent but much appreciated windfalls for American moralists) Graham addressed a tremendous stadium congregation in Albuquerque or some such city, and dealt heavy strokes. Well laid on. See where evil leads.

The cameras ranged over some of the faces of the congregation and I felt many of them had made their commitment to avoid thousand-buck call girls.

Some fellow (or woman, for there were many women at the Press Club that day) had sent up a question asking how Graham squared his hope of heaven with his wealth?

A graceless question, I thought, and not likely to elicit a fruitful answer so I cautiously approached the "apple pie" determined to see where the crust ended and the goo began.

An impossible project, of course, and because of it I missed several illuminations most likely, but have my own theory of national virtue:

Keep your eye on commercial pies. Evangelists love to say the nation is ripe for a moral revival, but that's just talk. If (piewise) the day ever comes you can tell the crust from the goo, you won't need an evangelist to tell you the millenium has descended upon our shores, and virtue has eastered amongst us.