WHEN MEMBERS of her group house debated the merits of prospective housemates, Jody Silvio said she put in a good word for one because "he had nice knives."

Life can be complicated in group houses, and kitchen arrangements make it more so. Even in a house of eight vegetarians, all of whom presumably share the same food philosophy, there can be eight different ways to layer spinach lasagna.

In group houses, as in many families, the kitchen serves as an emotional center, and its misuse causes arguments as well as laughs. In transient Washington--where the toaster oven disappears with the roommate that moves back to Toledo--people have learned to be flexible.

Those who share food, cook and eat together say the rewards are in the homey environment, as well as the financial savings. "It's wonderful when you come home from a hard day of work and find someone cooking up a storm," said Ken Wasch, a 31-year-old attorney who is collecting recipes used in his Reno Road house (they call themselves the Reno Roadettes), in the hopes of some day compiling a group-house recipe book.

And many group dwellers who cook together report that they eat better as a result. "If you're only cooking once a week, you can have fun with it," said Julie Miller, a reporter for Science News who lives on U Street with three adults and her 9-month old baby.

The group house can also recreate that back-home feeling. Every Sunday, five Georgetown University men--three of Italian descent-- who live together in Glover Park stage an afternoon supper, cooking up casseroles of baked ziti, lasagna or chicken cacciatore, inviting friends and professors over to eat.

A group's decision to eat separately may result not only from differing schedules, but differing food habits. Silvio, a special education teacher who works part-time making pa te' at Sutton Place Gourmet, said her vegetarian hairdresser roommate rarely partakes of Silvio's spicy concoctions. Kirsten McKay, who lives in Foxhall Village, said her two roommates are "very diet conscious," content to eat salads for dinner. She wants "a real meal with something from each food group."

And then there's the case of a vegetarian in a house of carnivores. Surprisingly, Larry Goldsmith, a lone vegetarian in a Takoma Park group house, said it works out quite well. When he won't be home for dinner, the house eats meat. Otherwise they eat vegetarian.

Whatever the eating arrangements, they're always different from house to house, and frequently change as people move in or out. Here then, is an all-purpose, group house, kitchen-arrangements checklist: * HOUSEMATE WANTED

Eating and cooking habits can be the decisive factor when choosing potential housemates. An immediate "weeder-outer," said Bob Kelly, a 31-year-old lawyer who lives with the Reno Roadettes, is "saying that we share food." Some may want the group house, but not the group food.

The opposite can happen, too. One woman decided her diet would be too limited if she moved into either of two houses on Capitol Hill. In one, the roommates wouldn't eat meat, in the other, a roommate was allergic to cheese and tomatoes.

In communal cooking houses, roommates have learned to be wary of interviewees who are more interested in cheap rent than group eating. When sizing up prospective roommates, vegetarians immediately become suspicious when they hear statements such as "I only eat hot dogs at ball games, and I love salad." * CHECK THE BACK YARD

One not-so-obvious reason for picking group housing over apartment living is that often there is garden space available. The back yard can even be used for animals. At an all-male Arlington house (now defunct), a live chicken named Chicken lived out back, laying one egg a day for the group. Besides the animal's contribution at breakfast time, "it was fun at parties," said one ex-roommate. * BRING KITCHEN EQUIPMENT

It's not only food that may be shared; there's also the divvying up of kitchen equipment--or the doubling up. Extras will be stored in basements, some never unpacked. At one point in its history, Goldsmith's group house had stockpiled four woks. Everyone at the Reno Roadette household owns a skillet, and the number of cheese graters has hit overload. (Repetition also prevails in the spice category, the Roadettes report; they have five tins of cloves.)

When nobody in the house has a crucial piece of equipment, one person often springs for it, taking it when he or she moves. Sometimes they inherit equipment. The Georgetown students' house was outfitted, in part, by neighbors who donated unused equipment from their garages. * MAKE CHARTS AND LISTS

Communicating in a group house is often done through notes, charts and lists tacked somewhere in the kitchen. If a resident is not going to be home for dinner, there's a sign-up sheet for that. If they wish leftovers to be set aside, their names must appear on the "Please Save Me Food" sheet.

Job wheels, chore sheets and the like are commonplace; the Reno Roadettes have a chart entitled "Do or Die," that details tasks assigned to each ("DS: Kitchen: Scrub floor, countertops, clean out refrigerator when necessary").

In a Greenbelt group apartment, an elaborate chart system was devised to counteract in-house food thieves. The chart listed housemate names down one column and names of food across the top. When one person would buy an item, he would mark a corresponding "B" under it. If he used the item, the notation would be a "U." At the end of month, B's and U's would be counted and pay-backs determined. * DIVIDE THE REFRIGERATOR

Apportioning refrigerator space can be a challenge for groups that don't cook or buy food together. Aside from "the masking tape option" ("You open up the refrigerator and there's a half gallon of milk with masking tape on it that says 'Joe's'," Chris Robling, press secretary for George O'Brien (R-Ill) explained), space can be allotted through individual shelves (Kirsten McKay and her Foxhall Village housemates each get a shelf) or by understood belongings ("The beer and Mountain Dew belongs to Mark; the diet soda belongs to me," said Glen Echo Heights resident Cindy Lynch).

Or, an entirely separate refrigerator may be the only solution. At a Capitol Hill group house, the refrigerator "always had 50 unidentifiable objects crammed in it," said a 27-year-old housemate. According to the housemate, who wished not to be identified, a woman who no longer lives at the house was rather untidy when it came to cold storage. Her tidier housemates got tired of searching for their own food, so they resurrected a refrigerator from the garage. "We told her we didn't have enough room," said the housemate. * GO SHOPPING

There are several modus operandi when it comes to shopping. Groups who cook together frequently assign one person a week to go the market. Or, everyone does "little shoppings," either from a master grocery list or not, jotting his name on a list followed by how much he's spent. At the end of the month, the bills are tallied and divided.

Group shopping can become a science. Five female roommates who live together in a Georgetown University on-campus apartment shop every Saturday en masse. Before their 10 a.m. expedition to the Georgetown Safeway, each roommate has to say what dinner dish she plans to cook that week and what ingredients she'll need. The list is compiled from there. Once at the market, one woman stays with the cart, dispatching her roommates to different aisles for products. Another woman pays the check, they each grab a bag and they all walk home together and unpack. "There generally isn't too much disagreement," said 19-year-old Patti deGroot.

Those who don't always cook together, but share the same staples, devise other arrangements. According to Robling, who lives with five men in Georgetown, his house works under "The Staple Program." Things had become disastrous when one roommate did all the shopping; a day and a half later, the house would run out of bread, milk and salt, said Robling. No wonder. The roommate's staple list included caviar and fancy canned sauces.

Now, Robling does all the staple shopping, and each man is on his own for the rest. Besides eggs, english muffins, milk and sugar, current house staples include Diet Coke, Honey Nut Cheerios and Chips Ahoy. (Robling said he also opted out of a sub-program in the liquor area where his roomates debated over the merits of Gordon's Gin over Black Label Scotch and if they should joint-purchase Old Grand-Dad in fifths or quarts.) * DEVELOP HOUSE SPECIALTIES

Among people in group houses interviewed, red meat was the least popular entree (even among non-vegetarians); casseroles, soups and other easily reheatable items were among the most popular dishes, and "The Moosewood Cookbook" was the most popular recipe reference.

With a house of four or six experimenting cooks, dishes are frequently not repeated. Except, that is, if the cook doesn't know how to make something else. Michael Gorges, a 24-year-old reference assistant at the Congressional Research Service who lives in Mount Pleasant, said his roommate's New Year's resolution was "not to make anything with macaroni anymore." There was one period, said Gorges, that the house was served tuna noodle casserole once or twice a week.

There may also be a concerted effort to develop house specialties. According to Shirley Maina, who lives in a five-person co-ed group house in Chevy Chase, one of her roommates brings home different wines for dinner, with the hopes of naming a suitable House Wine. * CLEAN-UP

Having to clean up someone else's kitchen mess is one of the prime sources of group-house contention. Often the tension builds until the kitchen slob is confronted head on. "Usually it the tension just comes out," said Julie Miller.

The clean-up philosophy in houses that cook communally seems to be split. Some groups feel that the person who cooks should also clean ("otherwise you use every dish in the kitchen when you cook," said Peggy Force, a 25-year-old utility specialist); other houses go by the rule that "If you cook, you don't clean."

To overcome sink messes, one local group house instituted fines of $1 for every dirty dish. The money collected went into common house supplies (paper towels, garbage bags). Within one week, the kitchen was spotless.

Untidiness may not always be the problem; sometimes a housemate can be too neat. Carl Catauro of the Georgetown/Italian house said one of his roommates is a neatnik. "We temper it," said Catauro. "He's one of the good cooks, so we don't bother him too much."

If there is a living checklist of group living, it's "El Nido" (the Nest), the eight-person vegetarian co-op in Mount Pleasant. It's dinnertime and Kurt Kuss has made vegetarian lasagna, a casserole of noodles, broccoli, cauliflower and eggplant, and there is a yogurt fruit salad. A guest has brought red wine. After pushing a button near the phone to buzz everyone in the house ("the El Nido Pavlovian response method," jokes Kuss), members of the house who are home this night (five, plus the guest) filter downstairs.

Cooking and eating is serious stuff at this house. An entire kitchen bulletin board devoted to "House Business" includes a food money chart ($16 per week), a co-op work chart (who works when at the 18th Street co-op the house belongs to) and a job wheel that looks straight out of summer camp. There are mason jars of lentils, split peas and garbanzos stacked in a cabinet, and two wall shelves' worth of spices.

"Nuclear waste comes up a lot," says Conrad MacKerron, of the group's typical table talk. Four of the housemates work in the environmental field and political discussion is common during the group's three-night-a-week dinners.

House residents agree that a community feeling is important for them. "I like to know the people that I live with. Dinner is the time to do it," says Karen Milgate.

More than two hours after the group has started eating, Milgate begins to clear the table. Soon, another roommate comes home for her "Save-A-Plate" dinner; Kurt strums his guitar in an upstairs bedroom; Michelle knits at the table with her feet on a chair. Dinner at home is over.

Here are some group house recipes: MICHAEL GORGES' FUDGE PIE (Makes a 9-inch pie)

Gorges' says everyone likes chocolate in his house; this brownie-like pie is a favorite. 1 cup sugar 1/2 cup butter 2 eggs, separated 2-ounces unsweetened chocolate 1/3 cup sifted bread flour 1 teaspoon vanilla 1 tablespoon rum, Amaretto, Grand Marnier or Cointreau or more to taste 1/8 teaspoon salt Confectioners' sugar, whole almonds and whipped cream for garnish

Sift sugar. Beat butter until soft. Add sugar gradually to butter. Blend until creamy. Beat in 2 egg yolks. Melt chocolate over hot water, cool slightly and beat into egg yolk-sugar mixture. Stir in flour. Add vanilla and liqueur. Set aside. Whip egg whites until stiff and add salt. Fold into batter. Bake in greased pie plate (no crust) at 325 degrees for 30 minutes. Optional step: To prevent pie from possibly cracking, place pie plate into a larger pan with a 1/2-inch of water and bake as directed.

Cool pie in plate for 3 hours. Sprinkle with confectioners' sugar. Place almonds around edge of pie. Serve with whipped cream. BETH PODOL'S PORK AND CASHEWS (4 to 6 servings)

This recipe is a regular at the 5-women group apartment at Georgetown University. 1 to 1 1/2 pounds lean pork 1 tablespoon soy sauce Cooking oil 5 or 6 garlic cloves, chopped 1/4 to 1/2 cup brown sugar 1/4 pound roasted cashews Rice for serving

Cut the pork into small narrow strips. Coat with soy sauce and let stand 10 minutes. Coat the bottom of a skillet or wok with oil. Heat until very hot, add garlic and cook until it begins to brown. Add meat to skillet and stir-fry until brown, about 10 minutes. Add brown sugar and cook until it melts and coats pork, about 2 or 3 minutes. Add roasted cashews and toss lightly with meat mixture, cooking about another minute. Do not overcook, or nuts will get soft. Drain on paper towels and serve over rice. TOM DAILEY'S QUICHE (Makes a 9-inch pie)

Dailey is a roomate of Chris Robling, the "Staple Plan" originator. 3 eggs, beaten 1 cup whipping cream 1/2 teaspoon basil 1/2 teaspoon marjoram Salt and pepper to taste 1/2 pound swiss cheese, grated Unbaked 9-inch pie crust 1/2 cup chopped vegetable of your choice: asparagus, scallions, green peppers or mushrooms, or a combination of two

Combine beaten eggs with whipping cream. Add basil, marjoram, salt and pepper and stir. Place grated cheese at bottom of pie crust and sprinkle layer of chopped vegetables on top. Pour liquid mixture into pie shell and bake at 350 degrees for 40 minutes. EL NIDO VEGETABLE CASSEROLE (4 to 6 servings) 3 medium potatoes 2 red onions 2 to 3 zucchini 1 medium eggplant 3 to 4 tomatoes 2 peppers (red, green or yellow) Salt, pepper and olive oil to taste Pitted ripe olives

Thinly slice all vegetables. In a casserole dish, starting with the potatoes, make alternate layers of vegetables, sprinkling each layer with salt, pepper and olive oil. Top with black olives. Bake for 40 minutes at 375 degrees or until all vegetables are cooked, but not soft.