THEY LONGED for goosefoot, purslane, dandelions and lambs-quarters. After a long hard winter and a dreary, vitamin-deficient diet, the early settlers eagerly awaited spring and the nutritious tonic of feasting on the first succulent leaves of these wild "salad greens."

We're luckier than the colonists. A good variety of leafy greens is available to us all winter. Once thought "downhomely," leafy green vegetables are moving uptown. Good cooks, alert to the nutritious nature and high vitamin A content of greens, cheer the migration, although Southern cooks have always known that greens are delicious and healthful.

Those anxious to brighten late winter menus will find a surprising variety of leafy greens at the supermarket and greengrocer's.

Collard greens are a stalky member of the large Brausica family. The deep, bluish-green leaves are stripped from the stalk for cooking. Collards are rich in vitamin A and ascorbic acid. Kale, like its relative, collards, is also rich in vitamin A. There are two main varieties of kale: Scotch, an early variety with curly leaves, and Siberian, which has flat, smooth leaves. Leaves are bluish-grey, and the younger, more tender leaves are best. l

Field, or upland cress is often found growing wild in low, moist lands. It also is cultivated. Its flavor is similar to cultivated watercress. It is, however, a much bigger, more sprawling and leafy plant and requires much longer cooking time than watercress. The deep-green leaves are most often used in salads or as a garnish. They also are excellent for soup. For a change of pace, they can be tossed lightly in a small amount of hot oil in a skillet, just until wilted and tender. These go well with almost any meat.

Spinach also is in abundant supply. The rich, dark green leaves are deeply crinkled, and need to be soaked in lightly salted water to draw particles to the bottom. Thoroughly rinsed spinach is excellent raw and in an almost endless number of recipes. It is one of the more versatile leafy greens. A small paradox about spinach is that while crisp bacon bits are tasty on spinach salad, spinach should never be cooked in pork broth, as other greens are. The flavors are simply incompatible.

Turnip greens also are available, though not as readily as kale because often the turnip tops are cut off the roots. These greens are excellent cooked alone, or with the roots. The same goes for beet greens. When beets with fresh leafy tops are available, they can be cooked separately or together. Mustard greens, originally from India, have a piquant flavor. The tender bottom leaves add zest to a salad, and the upper leaves are best for cooking.

Then there's cabbage. Although cabbage comes in "heads," it qualifies as a leafy green. It was grown in this country as early as 1669. The types of cabbage are red, green, savoy (which has crinkly leaves) and Chinese cabbage. Some prefer the delicate flavor of Chinese cabbage for slaw and salads. It has an elongated shape. Its leaves are compact and wrinkled.

There are a few basic rules to keep in mind when cooking greens. First of all, the younger the greens, the more tender they will be. Before cooking more mature greens according to recipe instructions, it is wise to blanch them. Pour boiling water over the cleaned greens, swirl them around, pour water off and proceed.

A very rough rule of thumb in cooking greens is that three pounds of greens require one quart of water. The amount needed to serve a particular number of people depends on the type of greens and their bulk.

Choose the youngest and tenderest possible. Pick them over, discarding brown or withered leaves and tough stems. Wash them thoroughly. This means plunging them in cold water and rinsing them thoroughly. And then doing it again and again until all traces of grit are removed.

If they're young and fresh, the greens can be simmered in salted water at a gentle but brisk boil just until tender. Do not cover the pot. Cooking them uncovered prevents their turning an unappetizing gray. The greens can then be drained and tossed with butter or a small amount of hot bacon fat for seasoning. Do not overdo it with the butter or bacon fat. The leaves should just take on a slight gloss. This is the super-simple way to cook greens.

To do greens in the traditional fashion, they should be cooked in a broth in which pork, preferably smoked shoulder, dry-cured bacon (known colloquially as "middlin' meat") or country ham has been boiled. These dry-cured meats do not give off much fat, but impart a wonderful flavor to the liquid and then to the greens. To cook greens in this traditional way, put a piece of pork or country ham bone into a kettle of water and boil it until the meat is completely tender and done. Remove the meat, add the cleaned greens to the broth and cook until tender. Very young greens can be cooked in as little as 15 minutes. But mature, less collapsible greens, such as kale and collards, may require 45 minutes or more. The amount of pork and water required depends on the amount of greens being cooked.

Cook the greens uncovered, until tender. Put a lid half-way over the pot, and set it on the back of the stove, allowing the greens to rest in the remaining broth, or "pot liquor".Greens can then be reheated in the broth and saved. True lovers of greens strain off the "pot liquor" and serve it in cups along with the greens.

Greens are usually served with meat such as smoked tenderloin, country ham, fresh ham or hocks. Greens are also good with fried or roast chicken. Cornbread is a logical partner to greens cooked in the traditonal way. Preparation can be as plain as a bowl of mustard greens cooked in broth, or as fancy as a spinach souffle. SPICED RED CABBAGE (6 to 8 servings) 2 1/2 pounds red cabbage 1/4 teaspoon powdered allspice 1/2 teaspoon powdered cloves 2 heaping tablespoons brown sugar 3 level tablespoons vinegar Salt and pepper to taste

Shred cabbage fine and put in cold water. Let stand 10 minutes. Lift out and drop into preheated, heavy pot. Add a tablespoon of sizzling bacon fat. Stir and then add spices, sugar, vinegar and seasonings.

Cover and simmer until cabbage is tender. (No more than 1 hour.)

This may be prepared ahead and stored in the refrigerator for at least three or four days. Reheat as desired. If serving the cabbage with bland meat, spices may be increased. A touch of red wine may also be added just before serving. BEET GREENS (6 servings) 3 cups cooked, chopped beet greens 1 tablespoon grated onion 1/2 cup light cream 1 tablespoon prepared mustard 2 tablespoons prepared horseradish 1/2 teaspoon salt 1/8 teaspoon pepper

Combine all ingredients and heat to serving temperature, stirring frequently. SPINACH RING (6 servings) 2 1/2 cups chopped, cooked spinach (about 2 1/2 to 3 pounds raw) 1 cup milk 3 tablespoons butter 3 tablespoons flour 1/3 teaspoon nutmeg 1 teaspoon grated onion 1 tablespoon lemon juice 2 eggs, well beaten 1 teaspoon salt

Mix ingredients together and pour into a well-buttered, one-quart ring mold.

Place in a pan of hot water and bake at 375 degrees until firm. Unmold on a hot round tray or plate, and fill the center with a creamed vegetable, or creamed seafood or chicken. Or bake in individual molds and fill with creamed chicken, shrimp or lobster and serve as a luncheon entree. DANDELOIN GREENS (6 servings) 2 pounds dandelion greens, chopped 1/3 cup all-purpose flour 1/3 cup melted butter 1 cup milk 1/3 teaspoon salt 1/8 teaspoon pepper 1/2 cup grated Swiss cheese 1/2 cup cracker crumbs

Arrange greens in two layers in a greased, 1 1/2-quart baking dish, spreading flour between layers. Combine butter or margarine, milk, salt and pepper. Pour over greens. Combine cheese and crumbs. Sprinkle over top. Bake in moderate oven (350 degrees) for 35 minutes. CHINESE CABBAGE WITH ONION AND ORANGE 1/2 cup sliced red onions 2 oranges 1 lemon 1/2 cup chopped green pepper 2 cups shredded Chinese cabbage 1/4 cup oil 1 teaspoon lemon juice 2 tablespoons orange juice 1 teaspoon salt 1/2 cup chopped green pepper

Choose oranges and lemon with thin skins. Cut off one slice of skin at both ends. Do not remove remaining peel. Slice fruit as thinly as possible. bCut slices in half. Remove seed (work on a plate to prevent loss of juice) Mix fruit and juices with cabbage, onion and peppers. Add salt, oil and lemon and orange juice. Mix well and pat down gently into bowl. Marinate in refrigerator for 2 hours before serving. TRADITIONAL RECIPE FOR GREENS (Collards, kale, mustard, turnip tops, etc.)

Put a piece of smoked pork shoulder or other dry-cured pork in a kettle of water and boil until meat is tender and done. Allow approximately 1/2 pound meat for a "3 pound mess of greens". Allow about 1 quart of water for every 3 pounds of greens. Remove meat and plunge cleaned greens into the boiling pork broth. Cook uncovered at a brisk but gentle boil just until greens are tender.