Bobby Doyle of Central Falls, R.I., one of five distance runners who came in from the cold of snowbound New England, easily won the 17th annual George Washington's Birthday Marathon yesterday.

In fact, he bettered by more than two minutes the old record for the moderately rugged course thourgh the Agricultural Research Center grounds in Beltsville, and made the feat look as easy as cherry pie.

On an ideal day for a mid winter race, Doyle traversed the 26-mile, 385-yard marathon distance - three 1 cops of a picturesque, rolling course through forest and farmland - in 2 hours 22 minutes 14 seconds. He finished a full 5:45, or more than a mile, ahead of Jeff Peterson, 21, of Springfield, who pleasantly surprised himself by coming in second (2:27:59) in his maiden attempt at a marathon.

Petersons good friend and sometimes running mate at George Mason University, Greg Colas, was the third man across the finish line, but he was not an official entrant. His time, unofficially, was 2:29:05, but his bid to make a retroactive entry was rejected by race officials.

The official third-place finisher was Mike Sabino, 38, of Baltimore, in 2:32:38. This was only his second race since surgery for a hernia, but Sabino finished among the top 10 in this event for the eighth conservative year.

A total of 418 men and 21 women went to the starting line, in front of the "log cabin" at the U.S. Department of Agriculture Farm. They ranged in age from 8 to 59, and came from 15 states plus the District of Columbia.

The top woman finisher was Janet Norem, 20, of Valparaiso, Ind., a sophomore majoring in biochemistry at Penn State. She finished in 3:09:30, 12 1/2 minutes better than her only previous marathon, at State College, Pa., last year, even though she has only been able to train 70 miles per week this winter.

"I'm not on a team or anything, so it's a little hard to do more than that," she said, looking up from a postrace meal of chili and hot dogs she was enjoying in front of a blazing fire in the Department of Agriculture cafeteria, where about 400 people congregated after the marathon. "This was a really nice race, especially for those of us who have been up north. With all the snow, we haven't seen grass in months."

The snow cover has receded enough to reveal broad stretches of straw-colored and muddy terrain as the runners made their way down Beaver Dam Road, past the NASA Goddard Space Center testing grounds, left on Springfield Road (where the aroma of the USDA hog farm gives added incentive to speed up the pace), and left again along Powder Mill Road, up a long incline back to the start/finish line at the front door of the "cabin".

This is not a speed course because it includes five modest hills (15 in all for the three laps), and the rural raodways are pitched and narrow as they meander through the rustic, tree-lined countryside. It is, however, a runner's course - full of pretty views and burdened by heavy traffic at only one brief stretch, at the entrance ramp to the Baltimore-Washington Expressway.

Doyle, 28, co-owner with his brother of a sporting-goods store in Pawtucket, R.I., knocked 2:04 off the previous course record of 2:24:18, set by Marshall Adams on a chill, windy February day in 1973.

There were no gusts to hold down times yesterday, only a slight headwind after the first turn-around. On a nippy but absolutely clear and sunny day, Doyle - representing the Johnson and Wales College Athletic Club - stepped ahead of Danny Kyle after 1 1/2 miles, opened a 50-yard lead in the fourth mile, and then steadily pulled away.

For the first two laps, Mark Stevenson, a midshipman at the U.S. Naval Academy, ran with Doyle, but he was using this only as a workout and did not officially enter. He dropped out, as planned, after 17 1/2 miles.

"I didn't know him, but we chatted about the wind and the course. He seemed to know it well," said Doyle, who has won four of seven marathons since taking up the distance two years ago. He was a two-miler ("8:59 best, nothing exceptional") at Texas-El Paso, from which he was graduated in 1972 after four years on a track scholarship.

"He (Stevenson) told me right at the beginning that he was only going two loops, and not to worry about him, but I thought he was pulling my leg," added Doyle. "I saw his 'Navy' sweat-shirt and figured you can't trust those Navy guys. My brother-in-law's a Navy man, and he's always pulling my leg."

But Stevenson - who did the same thing last year, but neglected to tell winner Max White of Alexandria that he was only out for two laps of exercise - kept his word, leaving Doyle to lap scores of runners the last eight miles as he accelerated out of sight of Peterson and all other pursuers.

A handsomely freckled 5-foot-9, 138-pounder with flaming red hair and beard, Doyle runs with a smooth and powerful stride. He holds his hands exceptionally high, but his head barely bobs and he treads lightly on the upper body, he gave no hint of ever faltering or breaking down.

With Stevenson along to help set the pace, Doyle covered the first two loops in 47:27 and 47:03. Alone, which is a difficult way to run, he did the last in 47:44. But he didn't regret the lack of competition to push him. "It feels kind of good to be that far ahead," he said. "I'll get my competition at Boston in April."