A former Washington Post pressroom trainee was awarded $200,000 in compensatory damages by an Arlington jury yesterday for injuries he suffered in a beating during a 1975-76 pressmen's strike at the newspaper.

Gerald R. Collier, 35 , of Fredericksburg had sought $3 million in compensatory and punitive damages in his civil suit against the International Graphic Communications Union and its Local 6.

During the nine-day trial, Collier's lawyer argued that five unidentified assailants wearing ski masks who beat Collier severely on the night of March 12, 1976, acted as "agents" of the union and its local at The Post.

The seven-member Arlington Circuit Court jury agreed, although the five men never were identified and no charges were brought.

David Rein, an attorney for Local 6, argued unsuccessfully that the union did not condone acts of violence that occurred during the strike and did not know the men who beat Collier.

"Our case consists entirely of saying we know nothing about this," Rein told the jury.

Collier, who was hospitalized several times for his injuries, now suffers from traumatic epilepsy and is unable to work, Collier's lawyer, Oren R. Lewis Jr., said in court.

Lewis contended that the five men were carrying out the union's goal of intimidating employes who went to work during the frequently violent strike. "They [the union] would not tolerate anyone working at The Post," Lewis told the jury.

Collier testified his assailants beat him with their fists, hit him on the head with a pipe, cut his chest, wrapped him in barbed wire and left him unconscious beside a country road.

The incident occured after Collier left work at The Post about 8:15 p.m. Collier testified he was followed by three men across the 14th Street Bridge, but lost them temporarily by speeding up to more than 100 miles an hour on Interstate Rte. 95. He finally was forced off the road near the Thornburg exit of I-95 in Spotsylvania County, where the beating took place.

Collier testified that one of the assailants identified him as a guard assigned to protect Post pressroom foreman James H. Hover, who was beaten in the paper's pressroom on Oct. 1, 1975, at the beginning of the strike. Collier was employed as a Wackenhut security guard before starting work as a pressroom trainee.

In a June 23, 1976, hearing, D.C. Superior Court Judge Leonard Bradman cited Collier's beating as "the single most vicious incident" in strike-related violence that led Braman to issue a permanent injunction against Local 6 picketing at the newspaper.

It could not be learned immediately whether the union will appeal yesterday's jury verdict. A hearing on post-trial motions in the case was set by Judge Charles S. Russell for July 20.