Open Monday through Saturday, 11 a.m. to 7:30 p.m. (coffee only, 10 to 11 a.m.); Sunday, noon to 6 p.m. No credit cards. No reservations.

JUST DON'T LISTEN to those people who tell you that museum food has to be hamburgers and gluey apple turnovers. Send them to the National Portait Gallery or to the Corcoran to show them what it can be and remind them that cultivating taste is part of a museum's function.

The National Gallery tried. It spent a great deal of money and hired reputable consultants to develop its new cafeteria and cafes. Dedication to good taste went into everything from the tray design to the napkin rings. James Beard sent his recipes.

But many of us would rather have back the old cafeteria, with its long-time staff and southern cooking that sometimes worked and sometimes didn't, but always gave you a fighting chance.

What we have now is a glittery hard-edge series of eating spaces that make more of an architectural statement than a culinary statement, the food being prettily garnished but bland at best.

To start with the buffet, where most people start, it is immediately apparent that something has gone awry if you watch the traffic pattern for a minute. Say you bring a spouse and two children. One adult wants a shrimp salad plate (probably a first-timer, since the $2.45 plate is just a small mound of tiny shrimp with a lot of celery, a deviled egg half, pickle, tomato and - I can't imagine why, except to fill out the plate - a mound of cottage cheese). That person waits in the cold buffet line, carrying a tray. The other adult, wanting roast beef from the carvery - because it looks appealingly rare and generous at $2.25 - waits in the carvery line, also holding a tray. They both pick up their trays again and stand in line - holding them - because she wants some creamed onions (acid-tasting from the can) and broccoli (frozen, chopped, unseasoned), he wants some soup (the bean soup is light-textured and chunky with ham, maybe the best dish of the day). They might be tempted at that point to change the shrimp salad for a tomato-sauced lamb shank, chicken pot pie with a flaky square of crust, or for rare rib roast garnished with onion rings ($2.35). but the turning back looks too formidable. They carry their trays, again waiting in line, to the dessert area, their arms getting tired unless they are veteran weight lifters. If only they knew ahead of time that the brownies were short on flavor and the pies long on cornstarch, they could have saved one queue.

Again they heft the trays, again to stand in line, for beverages. The splits of wine ($1.80) and beer ($1.20 and $1.75) tempt them more with each frustrating moment of waiting. Again, lifted trays, again waiting in line. But where are the children? That depends on how fast the fast-food line (fried chicken with french fries, $2.25; hamburger, $1.20; frankfurter, eighty cents) has gone.

Assuming everyone has managed to gather at the cashier, and that nobody's hand has slipped from the long wait with a full tray, the next task is to find an empty table. The sea of kelly green plastic tables with beige tops looks quite inviting by now. The silvery corrugated ceiling sets the room glimmering with tiny lights - too glaring for some tastes, but exhibiting a certain excitement. Time now to appreciate the simple white china, the careful parsley and pimiento garnishes. Time to see that the specially designed sugar envelopes match the no-longer-available paper napkin rings that once wrapped the long-gone linen napkins. Time to wipe the spots from the trays, the bits of stray food from the silverware, the greasy smudges from the glasses. Time to notice that the food is not bad - standard, underseasoned, essentially dull, but not objectionable. Not time to decide that you would like a cup of coffee after all, to go with your dessert. You would just have to wait in line again, after you had started back at the beginning to find a teaspoon.

The Concourse Cafe is another story - not a better one, not one with a happier ending, but one with another plot. Separated from the buffet by a low wall filled with a lavishness of flowers, its atmosphere is substantially different. Triangles of marble, skylit, glass-walled with a fountain of falling water behind the window, it has served as a preview of the East Building's architecture. Round marble tables with Plexiglas folding chairs are widely spaced. It is airy, spacious, blatantly sophisticated.

It is also outrageously noisy. Sounds bounce and echo and resound. This is no place to unwind and reflect on the world's masterpieces.

On the other hand, the service lately has been more prompt and less irritating than it was a year ago. And the food is attractive, actually rather lovely, if pallid tasting. The menu changes seasonally, the latest one being a choice of five main dishes - crepe divan, mushroom quiche, chef's salad and cold trout ranging from $3.50 to $4.50, and a fruit-cheese-pepperoni tray for two at $6.75 with a carafe of wine included. The most ambitious dish, the trout, is a presentable little fish with a pimiento stuffed olive slice for its eye, a layer of dill and pepper covering its body and overlapping cucumber and egg slices as its bed. Even the dill-sour cream sauce needs a dose of zestiness, but it all tastes fresh enough. As for the fruit and cheese, it is a handsome array of big purple grapes, fresh pineapple, watermelon and the like, with a couple of chunks of pedestrian cheddar, a big hunk of rather good pepperoni, and some totally forgettable bread and rolls. Not bad. Not particularly good. Some vague okay world of culinary middlebrowism. For dessert, sundses ($1.40) are probably the best bet, because the Watergate pastries ($1.50), if you examine the cart closely, tend to look the worse for wear. Coffee is a rewarding choice, it being served in a little pot with plenty for refilling. You can linger, reflect, retell your children, "Once upon a time there was, in the basement of the National Gallery, a cafeteria. It was a sweet old cafeteria, not fashionable or glamorous, but you could get grits there, and some grand old southern-style vegetables. And the gray-haired ladies who served you were proud of their pies and cakes . . ."