HILLSBORO, Ore., July 30— A man who prosecutors say was under orders from a top Hell's Angels leader was convicted today of murdering a woman, her twin 6-year-old girls and a family friend 17 years ago. 
The defendant, Robert G. McClure, 47, was sentenced immediately after the verdict to four consecutive life terms in prison. 
Mr. McClure had claimed that he had been framed by the bikers club. He sat impassively as the verdicts and sentences were read. His lawyer, Lisa Maxfield of Portland, said he would appeal. 
The jury in Washington County Circuit Court deliberated more than six hours over two days before returning the unanimous verdicts. 
Judge Jon B. Lund called the trial one of the "most egregious" murder cases he had ever heard. He told Mr. McClure that he had killed "four innocent people in a heartless and coldblooded fashion." 
Execution-Style Killings
On Aug. 7, 1977, Margo Compton, 24, was found dead in her home in the rural town of Gaston, along with her daughters, Sylvia and Sandra, and Gary Seslar, 19, the son of her boyfriend. Each had been shot in the head.
Ms. Compton's sister, Lynne Spieckerman of Gonzales, Tex., burst into tears when the verdict was announced. She and Bonnie Sleeper, who was Mr. Seslar's fiancee and who discovered the bodies, both hugged the prosecutors, Robert Hamilton and Robert Heard. 
"I believed in these guys," Ms. Spieckerman said. "They really knew what they were doing. When you kill children and innocent people, you just can't get away with it. You just can't get away with it." 
Mr. Hamilton said, "I'm relieved because this has been a long, long journey and I'm appreciative to so many, starting with the jury." 
The prosecutors contended that Mr. McClure had been under orders from Odis Garrett to kill Ms. Compton in retaliation for her testimony against several Hell's Angels in a San Francisco prostitution trial. 
Both Mr. McClure and Mr. Garrett, a leader of the Oakland, Calif., chapter of the Hell's Angels, were later imprisoned on drug charges. 
Facing Extradition
Mr. Garrett, who was also charged in the killings, is serving time in a California prison on a drug conviction but still faces extradition to Oregon. He was convicted in the San Francisco prostitution case after Ms. Compton testified against him.
Several prison inmates testified that the two had talked about their roles in the killings. The inmates said they had agreed to testify for the state because killing children violated their code of conduct. 
One prisoner testified that Mr. McClure had bragged about making Ms. Compton watch as he shot her daughters first and had claimed that they had died clutching their teddy bears. 
Mr. McClure, described as a hanger-on rather than a member of the biker club, maintained that he had been framed by the Hell's Angels because they wanted to protect the real killer. The defense claimed that the inmates who testified had done so to gain early release or better prison housing. 
Security at the suburban courthouse, about 15 miles west of Portland, was extremely tight through the seven-week trial. 
'Infamous Case'
More than 75 witnesses testified, including members of the Hell's Angels and the Aryan Brotherhood prison gang. Many were brought into the courtroom in leg irons, handcuffs and waist chains.
Lou Barbaria, a senior investigator with the New York State Police, has been following the trial from across the country. "It's an infamous case in the law-enforcement circuit," Mr. Barbaria said. He cited a Federal court case in New York in which the Hell's Angels involvement in the death of Ms. Compton had been admitted as proof of the club's viciousness toward those who testified against them.