Three years ago, a Department of Agriculture employee who is a former computer systems specialist for several companies decided he wanted to make it on his own as a consultant.He wound up sharing a tiny office in downtown Washington and, in the whirl of the area's consulting business, won his first contract a short time later.

Now, not that much unlike other success stories in the computer industry and its related spin-off fields, Robert Quinichett is at the helm of Sterling Systems inc., a McLean firm that posted sales of about $7 million and profits of more than $500,000 last year. Quinichett says his 300-employe company expects profits of $1.5 million on sales of between $12 million and $15 million in fiscal 1981.

Not bad for a man who grew up in difficult circumstances in Urbancrest, Ohio, with little money. His goal upon graduating from Ohio State University, he recalls, was simply to "make $5,000 a year and work the day shift" at a local plant.

Quinichett (pronounced kuh-nee-chee) now has a different set of goals, including entering the growing, international, computer services marketplace, winning major, contracts for lucrative government and energy work, and owning a firm with sales of between $50 million and $75 million by 1985.

In addition, he wants the company to ease its heavy dependence on government work by helping create computerized management systems for small business.

Quinichett has won a $6.1 million, four-year contract from the Federal Aviation Administration to monitor the modernization of the government's fight services program for noncommercial aviation. The FAA contract, won through the Small Business Administration, is the company's largest to date.

In addition, he has put together the Department of Energy's system for monitoring home heating oil prices nationwide.

Quinichett wants the company to be more that a service firm, and hopes to sell products -- although not computer hardware -- instead of time sharing. His products would be proprietary systems -- those he could license -- for small companies like the computerized business systems used by large corporations.

"There is a real shortage of professional talent to design systems tailored for a client's needs," he said in a recent interview. "Developing products for the commercial environment requires a major investment. You need capital to invest." In order to raise funds for growth. Quinichett hopes to develop an employe stock ownership plan.

For Sterling's first few years, Quinichett plowed much of the money back into the company. While sales rose from $400,000 in 1978 to $1.9 million in fiscal 1979 to about $7 million last year, profits lagged behind. Sterling showed a profit of only $12,000 in 1978, but that figure has risen to $44,000 in 1979 and more than $5oo,000 last year.

In this country, Sterling is developing computerized systems for members of the medical and legal professions, especially for operations that are too small to require their own hardware.

Quinichett is especially interested in developing veterianary programs because vets often have more than 20,000 clients. Thus billing and keeping up with rotating appointments are particualarly difficult. A vet using a computer terminal or printer in the office could more easily monitor drug inventories and bill clients, saving the costs of the labor-intensive work now performed by clerical help.

Internationally, Quinichett is looking seriously at technology-transfer programs that would bring computer systems in banking, for example, to underdeveloped but oil-rich countries, particularly in Africa.

But for all of Quinichett's obvious ambition, he admits that without federal minority business programs, which allowed his firm to bring in the contracts for its rapid growth, he would not be in the successful position he is today. Now only about half the company's work is based on gaining minority preference in seeking grants, he said. Minority group members make up about 46 percent of the Sterling staff. CAPTION: Picture, Robert Quinchett: surpassing his post-college goal of making $5,000 a year.