Small, informal collegiate track and field meets like the one yesterday at George Mason are fun sometimes, said George Mason Coach John Cook, because you never know who might show up.

Among a collection of Olympians, near-Olympians and national standouts, Olympic 800-meter champion Paul Ereng of Kenya, formerly of the University of Virginia, was the most notable performer at the Father Diamond Invitational, winning the 800 meters.

"I wanted to sharpen up a little bit," said Ereng. "The indoor meets are going to come during the next few months, and also I didn't run that many races last year because of illness and I want the feel of racing again."

Held up in the opening 100 meters because he was boxed behind Virginia's Ben Kurgat and St. Augustine's Ali Mahamed, Ereng ran around Mahamed at 110 meters, passed Kurgat at 210 meters and finished in 1 minute 51.68 seconds.

"It felt bad," he said. "I wanted to go faster but the person who made the pacing slowed everything down."

Ereng will return to George Mason Feb. 3 for the Mobil 1 Invitational.

For a meet attracting about 30 East Coast college teams and a handful of individuals not connected with teams, there was a surprising number of fast early season times.

Patrick O'Conner, a George Mason senior from Calabar High School in Jamaica and the fifth-place finisher in the NCAA 400 meters last year, won the 500 in 1:03.94. He will run the 400 in the Mobil meet.

O'Conner beat Trevor Graham (1:04.44), who is running for the Atlantic Coast Club and was on Jamaica's fourth-place Olympic 4x400 meter relay team in Seoul.

Another Jamaican Olympian, Vivienne Spence-Gardner, enjoyed a double victory. She won the women's 400 meters in 55.15, an event in which she hopes to qualify for the 1992 Olympic Games in Barcelona, and came back to take the 200 in 24.12. She ran on the 4x100 team in Seoul and will run the 200 in the Mobil meet.

"We're not blessed with the facilities in Jamaica like they are here in the U.S. and we know that we have to work for what we can," she said.

Jo White of Great Britain won the women's mile in 4:50.6 and is hoping to string together good performances this season in the United States so she may impress England's track and field federation and compete in the World Indoor Championships in March. In 1988 White won the 1,500 meters in the Olympic trials, but the federation often disregards trials in their selection process and she did not make the Olympic team.

"I missed the Olympics by four-tenths of a second and I've got to make myself much better so I'm not passed over again," she said.

Tony Barton of George Mason, last year's runner-up in the NCAA high jump championship, won that event in 7-3 1/4.