CAPITAL DINNER THEATER -- 1875 Connecticut Avenue NW (in David Lee's Empress restaurant). 882-5359.

FINIAN'S RAINBOW, Thursday through Sunday, until March 31. The show's informal, the dinner (before the show or after) is your choice of American (steak) or Chinese (shrimp tempura and something sweet-and-sour). The lease runs out at the end of the month, and the theater's looking for a new home.

ENCORE DINNER THEATER -- 1315 K Street NW (in the Almas Temple). 628-7973.

GUYS AND DOLLS, Wednesday through Saturday, until May 19. The quality of the dinner (your catered buffet: good roast beef, creamed seafood, rice or potatoes, a choice of vegetables and desserts) and of the show -- very close to professional -- takes the curse off the setting, which is like a high-school gymnasium with a stage at one side.

MELODY FARE DINNER THEATER -- 3821 Wilson Boulevard, Arlington. 525-4430.

PETER PAN, every day but Monday through June 15. Not the Mary Martin version, but a new adaptation of Barrie's classic by Ardith Cavallo, who with her husband, Laurence, runs the theater as well as the upstairs training in dance, music and the theater. The show's run has been extended for two months and an out-of-town theater has just bought rights to produce it. Meanwhile, dinner's buffetstyle, the largest spread of the three, and the show's professional sparkle is only partly explained by the fact that (uncommon in the field) all cast-members are paid. The setting, also, is the best of the three, in a converted restaurant, and the show benefits from the feeling that the theater has a home.

Back when towns had walls, there were troupes of players and jugglers and acrobats and clowns who came around from time to time to perform. It was their living, and they'd play in the inn or the town square or the church, wherever there was room.

Most often it was in or near the inn, and the landlord sold food and cups of mead and beer and wine to those who came for the spectacle.

What it was, really, was dinner theater -- in town, not outside the walls, or, now, the Beltway.

Dinner theater? I hear. Bad meal, bad show. Too expensive. Too far.

Well, there are dinner theaters inside the Beltway, at least three of them, and while they don't attract the attention that the KenCen, Arena and Folger do -- or even the dinner theaters out in the exurbs -- they do sing for their suppers almost every night, sometimes quite sweetly, giving aspirants an apprenticeship and the public supper and a show. Only one of them is set up in proper quarters of its own, and meals and performances vary widely -- even, sometimes, in different productions at the same theater. You may be fed a catered buffet or a menu fixe Chinese dinner or a rather lavish spread cooked on the premises; and you may run into a practically professional show or something akin to a summer-resort theatrical.

As for expense, if you put together the prices of a plate at a chain-swank restaurant and a seat at a first-run movie, it comes out about even with the dinner theaters' $12 to $15 -- and they throw in parking, which in this town is something.

Not to mention that if you go the dinner-by Marriott, show-by-Hollywood route, you'll miss seeing a Nicely-Nicely sing past a carrot chip on his soft palate, and wondering if the leprechaun is really the same guy who helped you out of a snowbank a couple of weeks ago, and lending an offstage nun a cigarette, and trying to guess what Captain Hook does during the daylight part of the day.

And you won't hear the 8:15 solo drowned out by the 9-to-closing disco band trundling its equipment in, or see a whole stage full of people standing about blankly while someone wrestles with a prop that suddenly won't do what it did in rehearsal, or see your waiter or waitress glow at discovering -- and showing the world -- "I can do that!"

You'll miss the crowd-scene peasant in the shiny black shose he forgot to change after his daytime job, and the agony as the music and the singer struggle to find, or create, a key in common.

And you won't get to sit down afterward with the entrepreneur and fine out why he or she -- yes, one of them's run by a woman -- thinks it's worth it to take on the headaches, heartaches and bellyaches of being producer, director and chief bankroller while, in most cases, holding down another fulltime job. Not to mention a social life, which in some cases in no longer worth mentioning.

And if you don't see the half-lit scenery-shift stumbles or hear their rumbles over the between-scenes music, neither do you catch the excitement thrown off by a stagestruck someone facing an audience, be it sellout or scattered. That's a lot to give away for a slicker show and a served supper.

Here are the three dinner theaters I've found inside the Beltway, and what you can expect to find at each: