SITTING down to a roast lamb surrounded by the first tender vegetables of the season is a rite of spring to be savored.

This is not to say that we cannot feast on lamb during the fall, winter and summer. In fact, "spring lamb"--or, more accurately, top-grade fresh lamb--could be on our tables year round. The supply is steady, thanks to modern shipping and breeds of sheep capable of giving birth twice a year.

The spring crop begins in February with lambs born in the mild climate of California's Imperial Valley, followed in March and April by lambs from Texas and Oklahoma. During the summer months, much lamb comes from the Midwest, and in the fall, mountain lambs from Colorado, Wyoming and Utah come onto the market.

What this masterful livestock management and distribution system does not take into account, however, is lamb's association through the centuries with festive occasions, particularly those with religious significance. Christians eat it for Easter, Jews for Passover and Moslems at the end of Ramadan. Since the first two of these holidays fall in the spring, Americans continue to eat more lamb at that time and less the rest of the year.

Not that U.S. consumption is ever very high. In this country people are remarkably indifferent to the traditions and flavor of lamb. To an enthusiast, it is inconceivable that anyone would prefer a hamburger, chicken leg or pork chop to a succulent slice of lamb, but this is indisputably the case. In 1982 Americans ate an average of only 1.5 pounds each, compared to 76.7 pounds of beef, 63.7 pounds of poultry and 58 pounds of pork. Lamb once placed somewhat higher on the ratings chart, but its popularity has declined since the turn of the century.

Several reasons account for this situation. Lamb costs a little more than comparable cuts of beef or pork, and a great deal more than poultry. Unfamiliarity is another explanation. Some regional cooking traditions exclude lamb almost entirely. Growing up in Texas, I hardly knew what lamb was; most of the lambs grown there are shipped off to the East and West coasts.

Of course, sometimes people who try lamb just don't like its distinctive taste. (Trimming as much fat as possible and replacing it with other oils before cooking can eliminate much of the strong flavor.) In addition, both our domestic and imported lamb are older when slaughtered than in many other countries; detractors say it borders on being mutton.

The U.S. Department of Agriculture says a sheep is a lamb until one year of age. "A 'spring lamb' could weigh up to 110 pounds," points out Mark Gann, a surgeon who raises sheep on his farm in Cockeysville, Md. His lambs are butchered at two to four months, when they weigh from 20 to 50 pounds, the flesh is pale and there is scarcely any visible fat.

Despite the USDA's generous age allowance, most commercial lamb is butchered at five to seven months. The smaller animals, known as hothouse or baby lambs, usually end up in New York City, where there is a heavy concentration of Greek, Middle Eastern and Jewish customers willing to buy this expensive delicacy. Here in Washington, Giant Gourmet's Someplace Special is taking special orders for whole baby lambs to be delivered in time for Greek Easter, which falls in May.

In other parts of the world, people are not so loath to eat lamb. In the Middle East, lamb and mutton are the two dominant meats. Kashmiri Hindus in India eat the Seven Dishes, all made of lamb, for weddings and other celebrations, and even Chinese cuisine makes room for lamb.

Lamb is a mainstay of the English diet; in her authoritative "Book of Housekeeping Management," published in 1861, Isabella Beeton wrote that lamb was "of all wild or domesticated animals . . . without exception, the most useful to man." Lamb is also found in Scandinavia, where the Finns offer sauna-cured lamb as a specialty. But the Europeans who qualify as the most passionate lamb eaters are the Italians, French and, above all, the Greeks.

During Greek Easter, lambs are roasted on spits throughout the countryside. One visitor reports that sometimes a whole lamb and pig turn in tandem on an enormous spit, so that the juices of the animal on top fall on the one below and the flavors blend.

In Italy, one sure sign of spring is the appearance of whole lambs in the markets. Especially prized are the tiny rib chops, offering one or two bites each. Coated in cornmeal or flour and perhaps parmesan, fried and sprinkled with lemon, they are sublime. In Rome, the traditional dish is abbacchio--a word many Romans use to refer to any young lamb, but that, strictly speaking, means milk-fed lamb of only three to four weeks that will fit in a roasting pan.

The choicest French lambs have grazed on the salt marshes near Mont St. Michel. Often the gigot or leg is roasted simply and presented at the table with a traditional accompaniment of white beans, but sometimes the preparation is more elaborate. A Julia Child recipe, for example, calls for boning the leg, stuffing the interior with a mushroom and kidney mixture, and enveloping the whole in puff pastry.

In the Middle East and the Caucasus region of Russia, lamb is often paired with dried fruits, pine nuts, cinnamon and allspice. These seasonings bring out its latent sweetness, in contrast to the European custom of emphasizing lamb's strong flavor with garlic, rosemary or oregano.

Like the Greeks, people in the Middle East are fond of roasting whole lambs on spits for special occasions. More commonly, however, lamb is cut into small pieces or ground and used sparingly along with grains and vegetables so that its delicate flavor permeates the whole dish. IMMOS (Lamb and Yogurt Stew) (4 servings)

Lamb cooked in yogurt or milk has been popular throughout the Middle East and in India for centuries. This version comes from Lebanon and translates as "in his mother's milk." 2 pounds lean lamb, preferably leg, cubed 2 medium onions, sliced Salt and black pepper 2 1/2 cups yogurt 1 tablespoon cornstarch 2 tablespoons of milk or water 2 cloves crushed garlic 1/2 to 1 teaspoon ground coriander 2 1/2 tablespoons butter Saffron rice for serving

Steam the meat with the onions and salt and pepper to taste, for about 1 1/2 hours or until extremely tender in an inch of water in a 3-quart pot. Meanwhile stabilize the yogurt so it will not curdle when cooked. This is done by placing it in a saucepan and adding cornstarch mixed with milk or water. Add 1/4 teaspoon salt and stir well with a wooden spoon. Bring slowly to a boil, stirring continuously in one direction only. Reduce the heat and let the yogurt barely simmer for 10 minutes or until it reaches a thick, rich consistency. Do not cover. Add the yogurt to the cooked meat and simmer gently for 10 to 15 minutes. Saute' the garlic and coriander in butter until the garlic just turns golden. Pour the mixture over the meat and yogurt, and serve with rice that has a little saffron mixed in. From "A Book of Middle Eastern Food," by Claudia Roden MARY ANN SCHAEFER'S GRILLED LAMB STEAKS (At least 8 servings) 5- to 7-pound leg of lamb 1/2 cup olive oil Juice of 1 1/2 lemons 3 cloves garlic 1/2 to 1 teaspoon oregano 1/2 to 1 teaspoon thyme Salt and pepper to taste

Have the butcher slice a leg of lamb into steaks about 1 inch thick. Brush the steaks with olive oil and juice of 1 lemon and let sit 1 hour or longer at room temperature. Rub with slightly crushed garlic cloves and sprinkle with thyme and oregano. Grill over coals or broil in the oven until cooked to desired stage, squeezing more lemon juice over the steaks from time to time. Salt and pepper to taste. LAMB BREAST WITH WALNUT STUFFING (4 servings)

This recipe is from the Caucasus region of Russia. The mixture can also be used to stuff a shoulder roast. 1 cup dried apricots or prunes, or a mixture of both 2 cups hot tea 2 cups coarse bread crumbs 1/4 cup chopped parsley 1/2 cup walnuts, coarsely chopped Grated rind of 1 lemon or lime 1 egg 2 tablespoons cream or vodka 1 teaspoon salt 1/2 teaspoon pepper Lamb breast, with pocket

Cover the dried fruit with hot tea and soak 2 hours or longer. Drain, remove pits if necessary and cut fruit into small pieces. Place in a bowl, add remaining ingredients and mix thoroughly. Stuff in the pocket of a lamb breast, press edges of meat together and tie if necessary. Cook in small roasting pan in a 325-degree oven for 45 minutes a pound. From "Madame Benoit's Lamb Cookbook" ROAST LEG OF LAMB WITH ORZO (8 to 10 servings)

This dish appears on many Greek tables at Sunday dinner, and the leftovers are then reheated for the evening meal. Serve with a salad of sliced tomatoes, cucumbers, green peppers and onions that has been dressed with olive oil, lemon juice, oregano, salt and pepper. 5- to 7-pound leg of lamb, trimmed of excess fat 3 3/4 cups dried orzo* 1 teaspoon olive oil Salt 6-ounce can tomato paste 1/2 teaspoon pepper Parmesan cheese Yogurt

Roast lamb fat side up at 450 degrees for the first 15 minutes, then lower heat to 350 degrees and cook about 12 minutes a pound (for medium rare) or until meat thermometer registers 150 degrees or to personal taste. Thirty minutes before lamb is done, bring 4 quarts water to boil. Stir in orzo, olive oil and 1 teaspoon salt. Boil 5 minutes. Drain, rinse in cold water, drain again. Remove lamb from pan when done. Wrap tightly in heavy duty or double foil and set on a plate. Add 6 cups water to roasting pan and mix to dissolve all drippings. Mix in tomato paste, plus salt and pepper to taste. Stir in parboiled orzo and add any juices that have oozed from the meat. Raise heat to 425 degrees, return pan to oven and bake 30 minutes or until orzo is tender and most of the liquid is absorbed. Taste and adjust seasoning. Carve the lamb and arrange slices in the center of a platter, with the orzo surrounding it. Pass parmesan and yogurt at the table as garnishes for the orzo. To reheat, cook orzo and meat separately at 425 degrees for 20 minutes.

Note: *Orzo is a type of pasta resembling rice grains and can be found in Greek or Italian groceries. From "Classic Greek Cooking," by Daphne Metaxas