Army Secretary Clifford L. Alexander Jr. has ordered the U.S. Military Academy at West Point to permit a cadet who was one of the first to reveal last year's cheating scandal there to graduate with the rest of his class.

West Point had refused to award a diploma or officer's commission to Cadet Richard A. McCollam after McCollam was given 80 demerits - more than half the maximum permitted a cadet in one year - for failing to register his car on the military academy's campus.

According to McCollam and his attorney, Army Capt. David Brockway, the refused diploma, the demerits, and a half-year of strict punishment McCollam has undergone stem from his efforts to reveal the full extent of honor code violations at West Point in the spring of 1976.

West Point denied McCollam's allegation. "The record simply will not support that contention," said an academy spokesman. "Additionally, it is not known by the authorities here that he has contended such."

When word of collaboration on a take-home engineering exam was first made public last year. West Point officials said the cheating was confined to about 50 cadets.

McCollam, who was one of 72 student honor board members at the time, said in a telephone interview yesterday that he told his superiors the real dimensions of the cheating were "quite large," and that the academy was "trying to make scapegoats out of those 50."

"I mentioned it to the (cadet) chairman of the honor committee," McCallom said. "I had just heard general rumors about it, but I had heard them from pretty reliable sources."

In subsequent weeks, according to several sources, McCollam was instrumental in the agitation that led to an expanded investigation of the scandal.

"There was a lot of bad feeling about 'those toublemakers' up at the Point," said Scott Sklar, an aide to Sen. Jacob K. Javits (R-N.Y.), who became involved in McCollam's case.

"There were cadets almost having lynch mobs for other cadets. Such passions between faculty, students, politicians, and Pentagon people were aroused that anyone who had something to do with that is going to have something hanging over his head for a long time," Sklar said.

"By my outspokenness, I did make a little name for myself within the hierarchy," McCollam said. "That was sort of festering" over the summer, and this year, he said, "the whole thing started up again."

Describing his last year at West Point, McCollam said he "can't think of anything worse." He was stripped of all privileges, confined to his room for each weekend between January and April, and made to march back and forth between two buildings with his rifle for a total of 70 hours as punshipment.

On May 19, McCollam was told he would be allowed to complete the school year and take his exams, but would not be given a diploma or officer's commission. The 80 demerits he had received for not registering his car gave him a total for the year of 155, four more than the maximum of 151 per year.

Brockway said, "eighty demerits, as far as I can tell, was the highest award of demerits for any offense given during the entire year." One cadet was given 70 demerits for assaulting a waitress and another 35 for smoking marijauna in barracks, Brockway added.

The West Point spokesman said 80 "is a large number of demerits. However, the board that considered his case - and it considered the individual and his disciplinary background - felt that this was the proper award."

Alexander, who will make a commencement speech at West Point today, entered the case when McCollam appealed West Point's decision not to graduate him. He overturned the decision late Monday afternoon. The Army secretary was unavailable for comment yesterday.