''These are the ways the fries are made in the U.S., and we don't have any plans to change,'' Mr. Riker said.

Burger King and Wendy's restaurants do not use beef products in their French fries, their corporate spokesmen said in interviews on Thursday.

Vegetarian groups had suspected there was beef flavoring in McDonald's French fries and petitioned the company and the Food and Drug Administration for full disclosure of ingredients with no success. Fast-food restaurants are highly secretive about their recipes, and it was only after the lawsuit was filed that McDonald's spokesmen widely acknowledged the beef ingredient.

''They would post these lists of their ingredients in their stores, but nowhere did they ever publicly admit that beef flavoring was used in the fries,'' said James Pizzirusso, who founded the Vegetarian Legal Action Network with other law students at George Washington University.

''Corporate America needs to pay attention to consumers who avoid certain food products for religious or health reasons, or because they have allergies,'' he said. ''They say they are complying with the law in terms of disclosing their ingredients, but they should go beyond the law.'' Vegetarian advocacy groups claim to represent as many as 15 million Americans. And while those groups are accustomed to confronting American corporations, the lawsuit is a watershed for the Hindus in the United States. Mostly first- and second-generation immigrants from India, with a smattering of American converts, they are estimated to number more than one million people. Until now, they have put far more effort into educating their children and building temples to perpetuate their religion than into pressuring the federal government or industry to accommodate their customs.

The lawsuit came about when the vegetarian law students connected with the outraged Hindus.

The students at George Washington University had drafted the legal complaint as a project for a class on legal activism, and were looking for a lawyer to file it. In Seattle, Harish Bharti, a Hindu lawyer, read about the secret ingredient in the article in India West and decided to sue.

India West heard about the ingredient from Hitesh Shah, a Los Angeles software engineer and a strict vegetarian. He had sent an e-mail inquiry about French fries to McDonald's, and received a reply from a customer service representative who wrote that McDonald's used ''a minuscule amount of beef flavoring as an ingredient in the raw product.''