Redskin fans got their first sample of Joe Gibbs' coaching last night long before Washington had finished defeating the Kansas City Chiefs, 16-10. They know something was different in the second period, when Gibbs called for a halfback option pass in a preseason game.

No matter that Terry Metcalf's throw to Art Monk fell incomplete. Many in the crowd of 32,488 at RFK Stadium began applauding at the sight of some daring in a Redskin offense that had been staunchly conservative for a decade.

From a rousing greeting for fullback John Riggins, back after a year's self-exile in Lawrence, Kan., to cheers for linebacker Monte Coleman, who scored Washington's only touchdown on a 28-yard interception run, Redskin partisans seemed to enjoy Gibbs' new look, even if both teams did make mistakes and play poorly at times.

In one half, the Redskins threw 19 passes. That was more than they would try in some games last season under Jack Pardee. And Gibbs says he hasn't advanced far enough with his offense to really open it up.

"I feel good about the game," he said. "We really hurt ourselves in the first half with mistakes, but the films should be very revealing. Our defense certainly played great."

In addition to Coleman's touchdown, Mark Moseley was perfect on field goal kicks from 39, 36 and 28 yards.

Kansas City managed only Nick Lowery's 53-yard field goal until the last two minutes, when quarterback Steve Kenney passed to Henry Marshall for a 32-yard score against Redskin reserves.

Washington's defense had struggled early in training camp, but coordinator Richie Petitbon probably won't have that many complaints after this game.

His troops limited starting quarterback Steve Fuller to 34 yards pasing before he left the game with an injured knee. And they didn't give Kenney, once a Washington quarterback, much more freedom until the final moments. The Chiefs gained 154 yards passing.

Washington's passing total was only two yards more, but Joe Theismann picked up 125 in the first half before giving way to rookie Tom Flick, who wasn't quite as sharp.

The crowd had about a half to judge many of the Redskin newcomers. Joe Washington carried twice, for six yards; Metcalf managed 22 yards on three tries. Riggins, a more familiar figure, went 17 yards. Defensive end Fred Cook started in place of Coy Bacon but didn't have a sack. Defensive tackle Wilbur Young was pursuing Fuller when the quarterback twisted his knee.

Mistakes limited both teams' scoring. On the Redskins' second possession, Monk fumbled at the Chiefs' 21 (he earlier had gained 32 yards on a reception).Before the half was over, linebacker Rich Milot had intercepted a Fuller pass, Kansas City's Ron Washington had lost a fumbled punt, tight and Rick Walker had fumbled a pass at the Chiefs' two and Kansas City's Mike Williams had lost the ball at the Redskin two.

All that nullified some exciting plays between the 10-yard lines. Monk, a second-year receiver, had six catches in the half he played, springing open repeatedly over the middle. Theismann threw his way often, appearing to ignore other targets.

Former Maryland star Lloyd Burruss, a candidate to become the Chiefs' starting safety, made an excellent interception. Before Walker's fumble could hit the ground, Burruss grabbed the ball and headed down field.

He appeared to be on his way to a touchdown before Joe Washington caught him from behind at the Redskin 25.And then Williams fumbled.

Virgil Seay, the Redskins' 5-foot-7 receiver-kick returner, almost had a touchdown, running a kickoff 68 yards before being caught.

Neither team could score until just before halftime, when Mosley was good on his first field-goal try as time ran out.

The kick was set up by Thiesmann's 20-yard pass to Monk, then a 15-yarder to Monk at the Kansas City 22. But the Redskins did not have time for another play and Moseley, who started poorly last season before shaking his slump, easily scored three points.

Lowery, the former St. Albans kicker who had a brief stay with the Redskins two years ago, tied the score on a 52-yard kick with 4:17 gone in the third period. A 25-yard screen pass was the key play in the drive that led to the field goal.

On the Chiefs' next possession, Kenney, from his 22, passed over the middle. Coleman grabbed the ball at the 28 and was in the end zone before the Chiefs could recover. Moseley kicked the extra point and Washington was ahead, 10-3, with 12:04 gone in the quarter.

The lead grew to 13-3 on Moseley's 36-yard field goal after Flick passed 14 yards to rookie Charlie Brown. A third-down pass to John McDaniel almost turned into a touchdown, but the ball was caught out of bounds.

Moseley's last field goal followed a Kansas City fumble. Kenney was sacked by Angelo Wells and Neal Elshire at his 17, with Wells recovering. Four plays later, Moseley was good from 28.

The Chiefs' touchdown was aided by a 15-yard penalty on Redskin rookie LeCharls McDaniel, called for unsportsmanlike conduct when he pushed Marshall after the Kansas City receiver had gone out of bounds with a 21-yard reception. Marshall then crossed over the middle and took in Kenney's toss for a 22-yard score.

Gibbs gave his young offensive linemen, especially guard Melvin Jones and tackle Mark May, considerable playing time. May, the No. 1 draft choice, still is learning to play left tackle and had problems with Mike Bell, the quick defensive end returning from a 1980 injury. Bell beat May's blocks for one sack and twice May was penalized for holding.

Considering its inexperience, the line held up well, giving Flick and Theismann good protection.

The Redskins gained 236 yards net, 135 passing. Gibbs had little reason to be pleased with his running game, which still lacks consistency. But he admitted the passing was pleasing, considering it is only midway through training camp.

Punters Mike Connell and Mike Kirkland didn't distinguish themselves. Connell averaged 39 yards on four punts and Kirkland almost 34 on four . . . Gibbs held out rookie guard Russ Grimm, but used another rookie. Joe Jacoby, in place of George Starke the second half . . . Rookie end Dexter Manley had one particularly impressive series, recording one sack and catching a running back from behind . . . Rain was forecast for the game, but didn't start falling until the final moments.