In the last edition of the Monday Morning Quarterback, a Purcellville, Va., doctor complained that government retirement systems encourage people to retire at 55 when they are in the prime of life. He said the public apparently isn't aware of this costly benefit, and he said his local golf course is crowded, even in midweek, with healthy, middle-aged federal retirees.

The doctor pointed out that Fairfax County recently tried to keep its 55-year-old school superintendent from retiring by offering him $157,000 a year -- half in salary and half in retirement benefits -- to stay on the job. "There is surely something wrong with a system that allows public servants to retire" that early, he wrote.

His comments produced lots of letters from angry retirees. Some said the doctor was stretching the facts by comparing the Fairfax situation to the federal retirement program. Others wondered what he was doing on the golf course with all those retirees. Here are some of the letters:

"If anything is 'wrong' it is the doctor's arithmetic. In order for a person to qualify for a retirement income of $75,000 at age 55 and assuming that he went to work for the federal government at age 18 he would need a high three-year salary average of slightly over $106,000. The government pay schedule and the Senior Executive schedule do not go anywhere near that high.

" . . . The doctor also cites that taxpayers earning $8 to $10 an hour are supporting federal retirees. Present federal employes are also supporting federal retirees. These same taxpayers are also supporting this doctor who can play golf with 'well to do' persons who are apparently posing, on the golf course at least, as high paid federal retirees." P.J.P, in Ocean City.

"I would like to find out from the doctor in Purcellville . . . how it is that I am not getting $75,000 a year. . . . I worked in government from 1941 to 1979, retired at 56 and still must work full time (at a non-federal job) to get by. It would be interesting to find out what the doctor expects to get at his retirement." S.P., in Greenbelt.

"Our hearts bleed for the doctor . . . whose weekday golf game is hampered by all those middle-aged and healthy government retirees cluttering up the course. But we hope he is more precise with the knife than he is with numbers!

"By juxtaposing the celebrated case of the Fairfax County school superintendent with government retirees in general, he seemed to be implying that many or most public service retirees get $75,000 a year.

"For a retired fed to get $75,000, his high three-year salary average would have to be $93,750 per year, which is off the scale. He would need to serve 41 years and 10 months to qualify for the maximum annuity -- 80 percent of salary.

"P.S. A friend of mine, who plays golf, tells me it's nearly impossible to get on the course on a Wednesday afternoon because the course is cluttered with doctors." L.J. Andolsek, President, National Association of Retired Federal Employees.

"The doctor had to be on the golf course himself to form the impression that it was crowded with 'middle-aged government workers'. . . . If he considers the term 'public servant' a mockery, he has not heard some of the terms people used to express their feelings (rightly or wrongly) about physicians." S.M.S., Carlisle, Pa.

"The Purcellville doctor who protested the 55-year-old retirement provision deserves some facts. . . . Someone retiring now, at top pay, with 42 years of service would receive $52,000 in annuity. . . . The average annuitant in 1982 was getting $12,500 a year." W.O.J., Washington, D.C.