Twelve years ago, Earl C. Brittingham was a veteran horse trainer looking for a new career after 15 years of working around the stables at the Charles Town race track.

Armed with only an eighth-grade education and a belief that "this was the country where you can have dreams," he applied for a part-time laborer's job with the General Services Administration, earning $1.90 an hour.

Over the next decade, Brittingham worked his way up the ranks at the Middle River supply depot near Baltimore. This year he became the first director of GSA's new customer supply center, directing an$11 million-a-year operation and earning $33,000 a year.

"Most of my coworkers at Middle River didn't have the incentive to better themselves," he said. "I was told: 'When you work in the federal government, you don't get nowhere when you work hard.' They tried to tell me to do the least if I got the job."

That part-time job offered no paid holidays, no vacation time "and the right of management to send you home early," Brittingham said. But he ignored the advice of his coworkers, hoping to win not only a full-time job but the benefits that would go along with it.

"If I worked a day, I wanted a day's pay for it," he said. "But I didn't want to do less than 100 percent."

The Middle River depot closed in 1981 and Brittingham survived the staff cutback there by transferring to the Franconia Supply Depot in Springfield. There he was put in charge of setting up GSA's first Furniture Reclamation Center, where agencies could save money by buying government furniture that had been repaired.

This year he was given a new challenge: setting up the agency's first customer supply center.

The center, and 13 others like it around the country, will replace the 48 retail-style stores that GSA operated primarily to serve customers who wanted to make small purchases of office supplies.

In this area there were 14 such stores, each with its own staff, expenses, management problems, and, in some cases, dissatisfied customers who would travel to the store only to find out that the product wasn't in stock.

GSA decided to replace the stores with the supply centers, which employes can call to arrange to have the purchases delivered.

A sampling of half a dozen federal offices found general support for the new system, although virtually everyone complained that it takes longer to get supplies than the 24 hours that GSA promises.

Earlier this year, GSA officials estimated the system will save about $6 million annually by fiscal 1986. Whether service will be sacrificed as a result remains to be seen.

"It's just like when I worked at the produce stand in Sparrow Point, Md., when I was six years old selling potatoes, watermelons and cabbage and the like," Brittingham said. "If you don't do good work , people don't want to come back and do business with you."

Senior GSA officials regard the switch from stores to a supply center as the most dramatic change in the way products are delivered to agencies since the GSA was created in 1949. Before then, each agency was responsible for making its own purchases.

To some extent, the new concept is riding on Brittingham's ability and personality. GSA Regional Administrator William F. Madison said that Brittingham was picked to run the operation because of his ability to "be creative" and "find ways to get things done that aren't snagged by the bureaucracy."

Said Brittingham: "The bottom line, is you can have the smartest person in the world, but if he don't like what he's doing then you're not going to get the job done.

"I try to encourage people working with me by showing them that you can move up from a WG-1. The drive comes from 'Mother Wit.' That's old terminology that means good, common sense."