The cost of bread more than doubled yesterday for shoppers at 250 Washington area supermarkets hit by a bakers' strike and left without their supply of house brand bakery products.

Representative for Giant's 121 stores and Safeway's 130 stores said they are searching for less expensive substitutes but so far haven't found any.

Both Safeway and Giant normally sell three loaves of their house brand bread for $1 -- or 34 cents a loaf. With those brands missing from the shelves, the lowest-priced bread at their stores is 87 cents for one loaf of Wonder Bread.

About 60 percent of the grocery dollars spent by families living in the metropolitan Washington area are rung up at Safeway and Giant.

Bakery sections in some of the chain stores were bare and glass showcases darkened, as a result of the Saturday night walkout by 450 members of Local 118 of the Bakery, Confectionary & Tobacco Workers, International Union of America. The strike was called when the union's contract expired and negotiations for a new one broke down.

The striking workers normally bake 40 percent of the bread and baked goods consumed in the Washington area.

Since Safeway and Giant had a two-day supply of bread on hand when their bakers left, there was no evidence of the strike in the supermarkets until yesterday.

So far, the chains have supplied shoppers' needs by increasing orders of bread from outside bakers who work under other contracts.

"We are not out of bread; we have six area bakeries supplying us," said a spokesman for Giant Food Inc.

However, stores do not have all of the bakery selection usually available. In the Giant supermarket at Ninth and O streets NW, for example, the two glass display cases for cakes, pastries and other sweets were empty yesterday. Signs were posted in the store explaining that, "Due to labor problems, we are temporarily unable to supply you with Heidi bakery products. We apologize for any inconvenience."

Safeway stores had signs offering similar explanations for their customers.

The chains traditionally have sold their house brand breads and baked products at lower prices than national brands because of lower advertising costs, food industry analysts said. In addition, the low-priced breads are used as loss leaders to attract customers to the stores, where they are likely to buy other merchandise as well as the less expensive breads.

Giant breads also are covered by the chain's self-imposed food price freeze, which is scheduled to continue through Aug. 2.

Neither Grand Union nor A & P Supermarkets are affected by the strike. Both of those chains have other suppliers for their bakery sections.

A Grand Union supermarket manager said yesterday that its house brand bread, L'ovenbest, is available for 43 cents a loaf, or two loaves for 85 cents.

The A & P house brand bread -- Marvel -- sells for the same price.

Shoppers at Giant and Safeway adjusted their purchasing habits to the higher house brand bread prices by buying less.

At the Giant in Northwest Washington, Carlene Johnson, who was shopping for her family of four, surveyed the stacks of Wonder Bread and pondered the prices. "I'm used to getting three loaves for $1," she said. "But at 87 cents a loaf, I guess I'll have to settle for two loaves this week."

The striking bakers left their jobs when they were unable to reach an agreement for a new contract with Safeway and Giant.

Wages, pension benefits and the chains' proposal for a bakers' assistant position are the major issues in disagreement.

The Heidi Bakery bakers were paid $8.93 an hour under the expired contract, Giant and Safeway have offered an increase of 85 cents an hour, but the bakers are seeking $1 an hour, according to spokesmen for the two chains.

Union business manager Carl Leitner wouldn't say what the union's position on wages is. He said that one of the critical points is managements proposal to add a new job classification that would pay only half as much as journeymen bakers now earn.

A spokesman for Giant said the company wants to hire a baker's assistant at each of the 45 Giant in-store baking centers to put cream and topping on pastry shells and to perform similar chores. Each center now has one full-time baker.

"There is not enough work for a second fulltime baker at each center, so we proposed one part-time assistant . . . who would earn $5.25 an hour to start plus part-time benefits," he said.