881-3636 Hours: 7 a.m. to 1:30 a.m. Monday through Saturday. Closed Sunday. Credit Cards: Not accepted. Prices: Most items $2.50 to $5. Complete dinner with beer or wine, tax and tip about $7.50 to $9.50 a person.

On the face of it, the Ambrosia is just another luncheonette, complete with glaring fluorescent lights, stainless steel and harried short-order cooks.

So why review it?

Because this luncheonette happens to serve some very good Greek dishes, and it adds a bonus: Through an archway is a pleasant little dining room, with candles and tablecloths, where you can enjoy those dishes in restaurant comfort but at luncheonette prices. Two people, if they order carefully, can have a more-than-adequate dinner for under $15.

The biggest sellers seem to be the gyros and souvlaki, and the popularity is deserved. Gyros is basically a pressed meat product, cooked on a spit that turns slowly, bought by restaurants from a limited number of suppliers. An important determinant of its quality is the fat content, with the poorer products intolerably greasy. The gyros at Ambrosia, shipped in from Chicago, is impressively lean, nicely flavored and served in mountainous proportions on excellent pita bread from New York.

Ambrosia's souvlaki, marinated and grilled chunks of pork tenderloin, can be just as good, flavored with plenty of garlic and oregano. And it's intrinsically less fatty than even the leanest gyros. But we've occasionally found the souvlaki too dry--quality control is not Ambrosia's strongest point.

If English is the international language, pizza is becoming the international food, so it's not surprising that a Greek restaurant does a credible job with it. The cheese and tomato are of good quality, and the crust is nicely crisp and chewy. If it's rolled out a little more stingily than you'd like, consider that this pizza is remarkably low-priced. (For an unusual twist, try it with gyros instead of pepperoni.)

Now for things more dinnerish. Forget the Ambrosia special. It combines gyros and souvlaki with dolmadakia in which the grape leaves are stuffed with an unpleasantly gummy and underflavored rice and a soujoukakia that tastes more of filler than meat.

But don't overlook the beef stefado, a big portion of well-trimmed (if slightly dry) beef cubes with onion chunks and good rice in a commendably complex tomato-based sauce flavored with a bit of rosemary and clove.

And each night brings a special lamb dinner--$5.45 with salad--that's hard to pass up. Most days, it's tender braised lamb cubes in a tomato sauce with cumin, cinnamon and bay leaf, served with good braised potatoes. On Fridays, it's lamb gouvetsi, the potatoes replaced by little Greek pasta pearls called orzo.

But perhaps the biggest dinner bargain is the Athenian chicken: half a big bird, nicely rubbed with oil, lemon and oregano and roasted to a golden brown. It tends to be overly oily (Why don't they drain the excess oil before serving?), but at $4.85 including a salad, one is tempted to overlook the fine points. (Hint: With all the dinners, pay 35 cents extra and have the pita bread instead of the rubbery roll that's included.)

A good light meal here is a Greek village salad, which includes feta cheese, anchovies and olives. Add an order of pita bread and a cup of good homemade soup and the total will be about $4.50. The three traditional Greek dinner pies--meat, spinach and cheese--are excellent, with light phyllo wrappers and zesty fillings. But the tarama salad is flavorless.

There are three Greek desserts, all made in house and all good. The baklava here is no delicate nibble. It's a hefty slab, sweet and wet, the overabundance of honey nicely offset by the profusion of cinnamon and coarsely chopped nuts, the phyllo crust still a bit crisp. The lemony cream custard is rolled in a good phyllo wrapper and soaked in honey, and the rice pudding, with what tastes like a touch of cardamom, is a good rendition.

Don't expect gracious dining or frills from the Ambrosia. Do expect friendly service, a warm, informal setting and some very good Greek cooking. And, when it's all over, you'll have experienced one of the better dining-out bargains around.