A lawyer who headed the Metro system's claims office for eight years was found guilty by a U.S. District Court jury here yesterday of receiving bribes in exchange for improperly awarding a contract to a friend that cost the transit agency $355,000.

James D. Loesch was convicted on two counts of receiving bribes and one count of conspiracy to commit bribery. The charges carry maximum penalties of 35 years in prison and $50,000 in fines.

Loesch, 58, worked for the transit authority from the time it took control of the area's bus lines in 1974 until he resigned in late 1981, dealing with claims by passengers and employes. He held a similar post for more than a decade with D.C. Transit.

During a six-day trial, witnesses said Loesch received a rent-free apartment and at least several thousand dollars in cash from Lester J. Stone Jr., 40, former head of New Horizons Consulting Agency, of Washington.

Records introduced at the trial showed that in December 1979 Loesch awarded a contract to Stone, who formerly sold art work as a vendor on Connecticut Avenue, to set up the firm to find jobs for disabled Metro employes who were receiving workers' compensation.

Metro comptroller William Boleyn testifed that the contract was placed without competitive bids and was not approved by senior Metro officials.

A key government witness, Michael A. Barnard, who formerly worked for Stone, testified that he was present when Stone paid a bribe to Loesch with $100 bills at a Northwest restaurant.

Assistant U.S. Attorney Theodore Shmanda said Stone was indicted in the case in January but now is a fugitive in Turkey. He said Barnard pleaded guilty to a lesser offense -- making a false application to a bank -- and was placed on five years probation by Judge Barrington D. Parker.

Loesch, who lives in St. Petersburg, Fla., did not testify at the trial, which was held before Parker. His lawyer, Thomas Abbenate, strongly attacked the credibility of Barnard and presented several witnesses who testified about the value of the services New Horizons performed.

Shmanda said Metro investigators assisted the FBI in the probe into Loesch's activity, which he said was the first case of substantial corruption involving a Metro official since the agency was established.