FOLLOWING THE successful reopening of the O Street Market, another food marketing center is nearing completion in the District. The Market House, the historic building on the south side of the 3200 block of M Street at Potomac Avenue in Georgetown, will be unveiled in late April or May. As many as 18 different food-related enterprises will be located on three levels inside the building. The developers also plan to sponsor outdoor sales of farm products two days a week.

Among the purveyors who have signed leases in the Market House are such well-know Georgetown names as Cannon's Seafood, Hudson Bros. Greengrocers, Georgetown Coffee, Tea and Spice. These will be branch stores. All three will remain in their current locations as well. The popular New York restaurant Pronto, which combines food and entertainment by making its pasta in front of customers, is scheduled to occupy the lower level of the building. The lease is contingent, however, on granting of a liquor license. There has been a hearing, but the ABC board has yet to grant or deny the application.

"Our goal is to have an active, exciting kind of place," said Courtney Lord of Western Development Corporation last week. Western and the Donohoe Construction Company took over the Market House Company last year. The company has a 24-year lease from the District to operate the national historic landmark as a market. The building itself dates from 1865 and the site was used as a market as early as 1795.

It may seem that Georgetown, which some feel already is a community of wall-to-wall restaurants and food shops, needs a reborn market house as much as most of us need whipped cream atop a banana split. Lord disagrees. "There are some products already available in a variety of places," he said. "Some of the best known are coming with us. What we are doing is putting the best together in one place and offering expert, personalized service item by item. We'll be open seven days a week from early morning until late in the evening.Not everyone will be open 12 hours a day, but they can sell food for on-or off-premises consumption.

"It will have a period feeling to it," Lord continued, "with tile floors, ceiling fans and lots of wood and awnings. The place hasn't been a market in nearly 50 years, but we want to make it look as though it never stopped operating." A tour of Europe and the United States to examine market projects, plus research on local markets of the past, convinced the developers that prepared foods as well as raw materials should be on sale and a mix of small stores rather than several large ones was desirable.

"We wanted the creme de la creme of local food purveyors and we wanted to squeeze them a bit to create a planned chaos of merchandising. They will have to hang products. Displays will have to be imaginative and, being limited, will require constant turnover. But it won't be a supermarket. The bakers will actually be baking, the butcher will be butchering, Lump's Que will be cooking barbecue in a nine-foot hickory pit. You'll be able to see them. And you'll be able to eat. Cannon's in going to have a raw bar and chowders. The greengrocer probably will sell fresh juices and prepared salads. The butcher's wife is going to fry chickens."

In addition to the restaurant, Lord said there will be seating on the mezzanine level of the market and at an outdoor patio overlooking the C&O canal. He stressed the eagerness of the firm, which is involved in two large developments nearby, to stimulate walk-through traffic over the canal and around the market. "With the development between here and the river, M Street is going to be the center of Georgetown," Lord said. "We felt the market could become a strong statement of what is needed here, a creative environment in what was a deteriorating area."

The developers contemplate home delivery runs from the market, a community bulletin board display inside and the sale of books and prints of historic Georgetown with profits going to charity. There will be parking nearby for restaurant customers.

Here is the roster of purveyors at this time. Ristorante Pronto is scheduled to operate on the lower level, with an entrance and display space on the street level. There will be at least eight entrances to the 7,600-square-foot ground floor level. An elaborately mounted flower and plant stand is intended to be the centerpiece of the market. Working back from the M Street entrance, shoppers will find Hudson Bros., the French pastries of Palais des Friandes, a display of dried fruits and nuts, a shop called the Creamery with dairy goods, Bassett's ice cream and strudel, preserves from Crabtree & Evelyn, the Coffee, Tea and Spice display, Georgetown Green's flowers, Crusties Bakery, a Jewish delicatessen, Lump's Que, Cannon's and Bromley Butchers. Three Brothers, an Italian delicatessen, will be located on the mezzanine.

A final decision has yet to be made on whether the Jewish deli will be a kosher operator from New York City or a local suburban firm.Two others expected to sign leases soon are the Empress Restaurant, which would sell Chinese groceries and some prepared food items such as cooked pork products and ducks, and Lansdown Caterers, which would provide a selection of freshly prepared foods suitable for reheating at home.

Possible themes for the remaining space include a wurst bar, a chili bar and a Spanish market.