Overall grocery store prices in the Washington area remained relatively steady last month-the first respite from an inflationary trend in food prices that began last September.

According to a report by the U. S. Labor Department yesterday, grocery prices here rose 0.1 percent in April compared with a nationwide increase of 0.8 percent. The figures were not adjusted for normal seasonal price changes.

Area supermarket prices had jumped 6.2 percent in the first three months of the year, which local food store executives had attributed primarily to soaring beef prices in all sections of the country as well as the adverse impact of winter weather on prices of fruits and vegetables.

Beef prices continued to rise sharply in April here and prices were higher for tomatoes, fresh or frozen fish and seafood and some fresh fruits.

To a large extent, however, these increases were offset by lower prices for most fresh vegetables, most pork items, cola drinks and poultry.

Cereal and bakery product prices declined 0.1 percent, average fruit and vegetable costs fell by 3.3 percent (compared with a 2.1 percent rise the previous month), and the price of meats, poultry, fish, eggs and dairy products rose overall about 1 percent.

Although government economists were unable to assess the impact in April of recent price rollbacks by Giant Food Inc., that action apparently contributed to the leveling off of area food costs.

Giant and Safeway Stores are the largest local food retailers, each holding about 30 percent of the market. Earlier this month, the federal government revealed that Giant had reduced prices on about 300 store items after discovering that resulting profit margins exceeded the administration's wage and price guidelines.

Most of Giant's price reductions were for dry and frozen foods rather than for meat and produce.

Beef remains the most volatile in price among goods sold at area food stores. According to the National Catlemen's Association, average beef prices are continuing to increase because weekly beef production has run 20 percent below the same period last year.

In the Washington area, a pound of ground beef that cost $1.19 in May 1978 now costs $1.59. The price of a pound of sirloin steak has jumped from $2.29 a year ago to $3.09 in April and $3.36 in May.

Area food prices are surveyed every month by the Labor Department's Bureau of Labor Statistics. A more complete survey of area consumer prices is issued every other month.