No matter how it's sliced, the turkey adorning Washington area tables this Thanksgiving represents one of the few bargains to be found in an era otherwise noted for rapidly-rising food bills and the overall food price inflation rate.

A sharp increase in turkey production is responsible for the present prices, officials said yesterday.

While turkey costs hover near or slightly below year-ago levels, the traditional trimmings have zoomed upward nearly 20 percent -- double the over all food price inflation rate.

Big birds weighing 16 pounds or more are priced about 8 percent below last year at most area supermarkets. Medium-sized turkeys tipping the scales at 10 to 15 pounds -- probably the most popular size -- cost essentially the same as last year.

Small turkeys weighing under 10 pounds are the only ones with higher price tags. But the 5 percent increase for small turkeys withers when compared to the 10 percent grocery increase recorded by the Consumer Price Index over the past year.

Prices for frozen turkeys at Giant and Safeway are set by a three-tiered system, similar to that used for eggs. The small Armour turkey, for example, cost 79 cents a pound; the medium, 75 cents a pound and the large, 69 cents a pound.

Last year that same turkey cost 75 cents a pound, regardless of size.

The staggered pricing also is used on the popular Swift's Premium basted "butterball" turkey, which was marked 99 cents a pound, small; 95 cents a pound, medium, and 89 cents a pound, large. Area chains sold all weights of the Swift's butterball turkey last Thanksgiving for 95 cents a pound.

One turkey industry official said yesterday that smaller turkeys are more expensive to grow per pound than larger turkeys.

"It is true that they eat less," said Lew Walts, executive vice president of the National Turkey Federation, a trade association based in Reston. "But the smaller turkey doesn't convert feed to meat as efficiently as a larger turkey," he said.

In effect, the cost of feeding a turkey is greatest when it is young and in need of higher-priced high-protein feed -- usually soybean meal complemented with corn, Walts said. As the bird matures, it needs less soybean meal and more corn.

Government and industry analysts agreed that increased production helped keep turkey prices down this Thanksgiving.

"We grew a record turkey crop -- 13 million head," said Walts.

The U.S. Department of Agriculture estimates that 1979 turkey production will be up about 10 percent over last year, with nearly 2.2 billion pounds of turkey trotting to market by the end of December.

Accoutrements for the Thanksgiving dinner -- unlike the star of the meal -- have risen substantially, according to a random sampling yesterday of some food prices.

Fresh cranberries, for example, now cost 49 cents a pound, up 10 cents over last year. Celery, a key ingredient for dressing, now costs 50 cents, an increase of 11 cents over last year. Four pounds of yams now sell for $1, up 20 cents.

One item that costs the same as last year is broccoli, available for 49 cents a pound.

The total cost for the four items: $2.48, compared to $2.07 a year ago. That amounts to almost a 20 percent increase in one year.

Pumpkins also have climbed in price. "But that is immaterial," a chain official said. "Because we're out of them anyway."