Elizabeth Horton is a prototype senior single cook. The 68-year-old Arlingtonian shops once a week (making a list and taking advantage of sales, coupons and house brands), uses minced garlic and onion to spice up dishes instead of salt and avoids processed foods by preparing frozen TV dinners from scratch.

According to the most recent Census Bureau statistics, there are almost 300,000 single people living in the metropolitan area, of which about 60,000 are over 65. And that figure is likely to grow substantially in the next few decades as the U.S. population becomes increasingly older. By the year 2025, predicts the Census Bureau, the number of persons 65 and older will be more than double what it is today.

That means that there will be more people like Horton who are faced with "empty nests," restricted budgets and special dietary needs -- not to mention the ageless dilemmas of buying and cooking for one that may be further aggravated by the death of a spouse, immobility or a degenerative disease.

This looming population has caught not only the attention of a number of health experts who are looking closer at the special nutritional needs of the elderly, but food marketers, who are realizing that baby boomers won't be stockpiling Haagen-Dazs forever.

A 1982 survey done for the Food Marketing Institute, for instance, showed that those between 60 and 80 don't have a lot of extra money, are interested in well-balanced meals low in sugar, salt and fat, complain that the portion sizes of prepackaged meat and produce limit their choices and don't like coupons but use them anyway to stretch their budgets.

In addition, a 1985 FMI trend report indicated that shoppers 65 and older shop less frequently than the rest of the population and are more likely than other groups to shop in the morning.

Vivian Kemerer, a 62-year-old Wheaton woman who shops once a week at Magruder's, tackles the problems of cooking for one by planning ahead. Like Horton, she prepares larger quantities than she needs for one meal and freezes the rest in portion-size packages.

For instance, Kemerer makes a pot of goulash with ground beef, macaroni and tomatoes canned from her back yard garden and puts them in Seal-A-Meal bags before freezing. Or she'll wrap up a cut-up chicken, freeze the pieces separately and defrost them part-by-part, perhaps cooking the breasts with her home-canned tomatoes and a touch of white wine. In addition, Kemerer frequently makes stir-fries to increase her vegetable consumption and to use up leftovers.

But like other astute shoppers, Kemerer realizes that coupons aren't always a bargain, especially if they're for items she doesn't ordinarily use or large container sizes that will lead to wasted food.

Mary Doran Evans, a home economist with the Human Nutrition Information Service of the U.S. Department of Agriculture, offers the following suggestions for thrifty and healthy meals for single older folks:

*Take advantage of the bulk foods departments in area supermarkets. They offer the advantage of personalized portions and are often -- but not always -- less expensive.

*Watch out for expensive convenience items such as frozen dinners and vegetables in seasonings and sauces that are often high in salt and fat. Make your own frozen dinners, and if buying frozen vegetables, buy those in large bags and use as much as you need at a time.

*Save money by purchasing cereal in medium or large boxes instead of the small individual boxes, by adding nonfat dry milk to casseroles and by slicing meats, cheese and chicken yourself instead of buying them precut.

In addition, the following services are available for elderly consumers: Support Groups

Widowed Persons Service: According to Audrey Markham, a consultant/organizer for the services and president for the Northern Virginia Widowed Persons Service, men are particularly vulnerable after the death of a spouse, since frequently they have never cooked before. Besides outreach services and discussion and activity groups, Widowed Persons Services hosts Brunch and Lunch Bunches, potluck dinners and cooking demonstrations at area widows' homes. Call 560-1115 for information.

Offices on Aging: Under the Older Americans Act, people over 60 (and their spouses of any age) who are socially and/or economically disadvantaged receive hot lunches. Served at numerous nutrition sites throughout the metropolitan area, the meal is free, although contributions of any amount are encouraged.

The nutrition sites also provide elderly consumers with periodic nutrition education and shopping tips, health screening, recreational activities and sometimes transportation to and from supermarkets. According to Kathleen Peterson, a nutrition site dietitian for the District, sometimes participants are taken to the D.C. Farmers Market or to discount food stores such as Basics or Price Chopper, where they shop jointly and split large packages.

Free hot lunches are also delivered in the District to the housebound who are economically deprived, according to Tanya Agurs, nutritionist at the D.C. Office on Aging.

For more information on local nutrition sites, call: Alexandria (838-4822); Arlington (558-2341); District of Columbia (724-5626); Fairfax (691-3384); Montgomery County (468-4443); Prince George's County (699-2695).

Meals on Wheels: Delivers hot lunches and cold snacks to area residents for a fee. For information on programs in the District, Maryland or Northern Virginia, call 434-1922 between 9 a.m. and 1 p.m. weekdays. Delivery Services

The following area supermarkets and companies will deliver groceries:

Broadbranch Grocery, 5608 Broadbranch Rd. NW., delivers groceries within a five-mile radius of the store. Delivery charge of $1 for orders under $20. Call 966-5656.

Brookville Market, 7027 Brookville Rd., Chevy Chase, Md., delivers groceries in the Chevy Chase area. Delivery charge of $2 for orders under $35. Call before noon at 652-2793.

Clover Market, 5014 Connecticut Ave. NW., delivers groceries to consumers in Upper Northwest and Chevy Chase. Minimum order $25, $1 delivery charge. Call 363-1717.

Glover Park Market, 2411 37th St. NW., will deliver a minimum of $20 worth of groceries to consumers in the Northwest quadrant. Call before noon and the groceries will be delivered that afternoon. No charge for delivery, but groceries are somewhat more expensive, according to owner Kimberly Koo. Call 333-4030.

Larimer's, 1727 Connecticut Ave. NW., will deliver a minimum of $25 worth of groceries. Delivery charge of $3 for all orders. Call 332-1766.

Neam's, 3217 P St. NW., charges $5 for delivery for orders under $30, no charge for orders over that amount. Call 338-4694.

Nothing Fancy Produce, 3316 11 St. NW., will deliver a full line of fresh meats and produce (no canned or boxed products). No minimum purchase necessary. Call 333-4030.

Top Banana, a Prince George's County supermarket delivery service that caters to senior citizens and the homebound, will deliver to residents of upper Northwest, most of Montgomery County and all of Prince George's County. The service has its own warehouse with 4,700 items in stock. No minimum orders, but there is a $4.50 delivery charge for senior citizens and the homebound, $5.50 charge to the general public. Orders must be placed Monday and Tuesday between noon and 8 p.m. for deliveries made on Thursday and Friday of the same week. Call 888-1201.

Washington Grocery Service shops at the Davenport Street Safeway and will deliver to anyone within the District. Delivery charge of $6 for grocery orders up to $50, $9 for orders up to $75, $12 for orders up to $100, $15 for orders between $100 and $200. Place orders between 9 a.m. and 1 p.m. Monday through Saturday. Call 797-7744. Other Services

Giant: The chain publishes a Special Diet Alert booklet that identifies products for special dietary needs. Giant also has a special program that provides pricing and product information for the deaf and hearing impaired. Call 341-HEAR for more information.

Safeway: The chain has no- or low-sodium and no- and low-sugar programs that identify products via shelf tags that fit those categories. Meat department personnel are instructed to provide smaller portions (such as one pork chop) upon request, according to consumer affairs advisor Jane Ratti. In addition, Safeway has begun selling more produce by the pound as well as produce in smaller quantities (such as half heads of cabbage).

According to Ratti, the chain is also in the process of putting larger unit price tags on bottom shelves for better visibility.

Also, some Safeways will provide additional personnel and individual service on specified days for senior citizens who wish to shop in groups. Call Jane Matti at 731-6803. Publications

These are free to the public unless otherwise noted:

"Shopping Sense for Seniors," published by Giant Food and available at all area stores.

A variety of Safeway Nutrition Awareness Program (SNAP) pamphlets deal with issues pertaining to older consumers, such as "Consider Sodium and You," "No Bones About It: Osteoporosis is Serious Business," "Diabetes: Questions and Answers," and "Cooking for One? Cooking for Two?" Available at all SNAP centers in Safeway stores.

"Eating for Your Health," a brochure published by the American Association of Retired Persons. Write to AARP, Health Advocacy Service, 1909 K St. NW. 20049.

"Good Eating: An Older Consumer's Guide to a Healthful Diet on a Low Budget." Send $1 to Blue Cross/Blue Shield, 1709 New York Ave. NW. Washington D.C. 20006.

"Age Pages" that discuss shopping, cooking and nutrition. Send a postcard to National Institute on Aging, Information Office, Bldg. 31, Room 5C35, Bethesda, Md. 20892.

These recipes for braised turkey breasts and pot roast get a lot of mileage dollar and food-wise. The turkey breast recipes are from a soon-to-be published USDA publication called "Making Food Dollars Count: Thrifty Meals for Two." BRAISED TURKEY DRUMSTICKS (Enough for 3 meals)

2 1/2 pounds turkey drumsticks

1/8 teaspoon poultry seasoning

Salt and pepper to taste

1 1/2 cups water

Brown drumsticks in a skillet for about 15 minutes. Sprinkle with seasonings and add water. Bring to a boil, reduce heat, cover and simmer until tender, about 1 1/2 hours. Turn drumsticks halfway through cooking. Spoon off as much of the fat layer as possible. Save 1/2 cup cooking liquid for making gravy (recipe follows).

Separate meat from skin and bones. Dice and save 2/3 cup for Turkey Spanish Rice. Dice and save 3/4 cup for Turkey Potato Salad. Save remainder of turkey for Braised Turkey Drumsticks with Gravy (below). BRAISED TURKEY DRUMSTICKS WITH GRAVY (2 servings)

1 tablespoon flour

1 tablespoon water

1/2 cup turkey cooking liquid

6 ounces turkey meat

Mix flour and water until smooth. Stir into turkey cooking liquid. Cook, stirring constantly, until thickened, about 2 minutes. Serve over braised turkey. TURKEY POTATO SALAD (2 servings)

3/4 cup diced turkey

1/4 cup chopped celery

1 cup cooked, peeled and diced potato

1 tablespoon chopped onion

2 tablespoons chopped green bell pepper

3 tablespoons mayonnaise

1 teaspoon prepared mustard

1/8 teaspoon salt

Mix turkey, celery, potato, onion and green pepper. Mix mayonnaise, mustard and salt. Mix lightly into turkey mixture. Chill and serve. TURKEY SPANISH RICE (2 servings)

1/4 cup onion, sliced

1/4 chopped green bell pepper

2 tablespoons chopped celery

1/4 uncooked rice

1/2 teaspoon margarine

8-ounce can stewed tomatoes

2/3 cup diced turkey

1/4 cup water

1/4 teaspoon chili powder

Salt and pepper to taste

1 bay leaf

Cook vegetables and rice in margarine in a small saucepan until onion begins to brown, about 4 minutes. Break up large pieces of tomatoes and add tomatoes with their liquid plus remaining ingredients to rice mixture. Bring to a boil, reduce heat, cover and cook slowly until rice is tender, about 25 minutes. Stir as needed to prevent sticking. Remove bay leaf and serve. POT ROAST (Enough for 3 meals)

1 tablespoon butter or margarine

2 pounds top or bottom round, brisket, blade, chuck or rump roast

1 cup water

1 bouillon cube, preferably low-sodium

1/2 teaspoon thyme

1 bay leaf

1 small onion, studded with 2 cloves

1 carrot, cut in chunks

1 potato, halved

1 tablespoon flour

1/4 cup water

Heat butter and oil together in a heavy saucepan. Brown the meat on all sides in the fat. Add water, bouillon, thyme, bay leaf and onion. Bring to a boil, lower heat, cover and simmer until fork tender, about 2 hours and 15 minutes. Turn occasionally while cooking.

During the last 45 minutes of cooking, add the carrot and halved potato. When meat is done, skim the fat from the gravy.

Remove meat and vegetables from the pot. Divide the meat into 3 equal portions. Reserve 1 portion and freeze or refrigerate the other 2 for Open-Faced Pot Roast Sandwiches and Pot Roast Hash (see below).

To make gravy, mix flour into water, stirring to remove all lumps. Whisk mixture into defatted cooking broth and cook over medium heat until thickened, stirring constantly. Remove and divide into 3 equal portions. Reserve about 1/3 cup and freeze or refrigerate the remaining gravy for sandwiches and hash.

To serve pot roast, slice meat 1/4-inch thick. Surround with carrots and potato and pour over gravy. Pot Roast Sandwich

Defrost one of the 2 remaining pieces of pot roast and slice 1/4-inch thick. Heat gravy. Place meat on top of bread and pour over gravy. POT ROAST HASH (1 serving)

1/2 cup diced pot roast

1 small raw potato, cubed

1/4 cup diced onion

Salt and pepper to taste

1 1/2 teaspoons butter

1 1/2 teaspoons oil

1/3 cup gravy

Combine pot roast, potato and onion together. Season to taste. Melt butter and oil in a small saucepan. Add pot roast mixture and cook over medium heat until a crust forms on the bottom. Turn and cook on other side until brown. Total cooking time should be about 1/2 hour. Turn hash pancake onto a plate and serve with reheated gravy.