Randy Bullock kicked a 41-yard field goal as time expired, and the Texans rallied from a 21-point deficit in the second half for a 31-28 victory over the Chargers on Monday night.
Brian Cushing returned an interception 18 yards for the tying touchdown with 9:30 to play for the Texans, who roared back from a 28-7 deficit late in the third quarter to spoil the debut of McCoy, the offensive guru hired to revitalize a stagnant franchise.
Matt Schaub threw a tipped interception on Houston's first play of the season, but recovered to pass for 346 yards. Owen Daniels caught two TD passes and Garrett Graham had another, while Andre Johnson caught 12 passes for 146 yards in the final game of the NFL's opening weekend.
Houston's powerful defense shut out San Diego over the final 25 minutes, and Schaub engineered the final 36-yard drive to set up Bullock, who coolly nailed his first NFL field goal.
Philip Rivers threw four touchdown passes as the Chargers gave their fans a tantalizing start under McCoy. They also got an agonizing reminder of last season under fired coach Norv Turner, when San Diego blew five halftime leads.
"You lose this way, and it stings a little more," Rivers said. "It's disappointing we didn't finish the game, because we had control. You've got to play all four quarters."
While the Chargers showed promise, the Texans began a season of Super Bowl aspirations with a gritty comeback befitting a defending two-time AFC South champion club that got off to an 11-1 start last season.
Ryan Mathews caught a 14-yard TD pass on San Diego's first snap, while Eddie Royal made two TD catches and Vincent Brown had another for the Chargers during an auspicious start in the first three quarters for McCoy.
He was hired away from division rival Denver to jump-start a team that has missed the playoffs for three straight years, leading to the dismissal of Turner and general manager A.J. Smith after the Chargers' first losing season since 2003. In last year's lowlight, San Diego blew a 24-0 halftime lead in its last Monday night game against McCoy's Broncos last October.
"We've just got to keep the pedal down," Mathews said. "You can see we can put up points, and our defense is looking great."
San Diego led 7-0 just 15 seconds into McCoy's tenure, thanks to an interception on Houston's first play and Rivers' TD pass on the Chargers' first snap. San Diego had a 14-point halftime lead and stretched it to 28-7 early in the third quarter, but Houston's offense finally clicked decisively.
San Diego managed just 90 yards in the second half, and the turnover-prone Rivers made yet another big mistake late in an otherwise solid game.
Cushing came up big in his first game since missing most of last season with a knee injury and then signing a six-year, $55.6 million extension last week. Rivers' under-pressure throw was snagged by Cushing, who got up from his diving catch and rumbled into the end zone.
After both teams punted, Schaub got the Texans in position for Bullock, a fifth-round draft pick last year who missed all of his first season with a groin injury.
The former Lou Groza Award winner at Texas A&M didn't miss, celebrating the kick with his new teammates and a vocal bunch of red-jerseyed fans who took over the sections behind Houston's bench.
In front of a Qualcomm Stadium crowd that bought just enough tickets to avoid a local television blackout, McCoy's tenure got off to a spectacular start on the first two snaps from scrimmage.
Schaub's first pass was tipped into the air by Jarret Johnson, and 330-pound defensive tackle Cam Thomas gathered it in. The San Diego crowd was still cheering when Rivers threw down the Houston sideline to Mathews, who dived in for a score.
Although Houston tied it later in the first quarter on Daniels' first TD catch, San Diego's defense mostly corralled Schaub and running back Arian Foster, who managed just 57 yards.
Rivers looked comfortable early on in McCoy's latest version of an offense that was tweaked for Tim Tebow and Peyton Manning in Denver in the past few seasons.
Rivers took most of his snaps in a shotgun, and San Diego used short drops and quick routes to keep Rivers out of trouble after he took 49 sacks last season.
Rivers hit Royal from 6 yards early in the second quarter, and he set up Brown to make an outstanding play with 26 seconds left in the half.
Brown, who missed last season with an ankle injury, dived at the corner of the end zone with the ball in both arms, barely clipping the pylon as Johnathan Joseph pushed him out of bounds.
Rivers went right back to work after halftime, moving the Chargers 80 yards for a short scoring pass to Royal. Houston responded with a long drive capped by Graham's TD catch.
Houston got another boost early in the fourth quarter when Thomas got a 10-yard penalty during a field-goal attempt for unnecessary roughness against Houston's center, giving a first down to the Texans on a new rule for this season. Daniels caught his second TD pass on the next play from 9 yards on the next snap, cutting San Diego's lead to seven points with 14:44 to play.
The Texans then successfully faked a punt with 12 minutes left, converting a fourth-and-1. Although Houston had to punt three plays later, Cushing made his tying interception on San Diego's next offensive snap.
Houston played without new safety Ed Reed, who isn't quite ready to return from offseason hip surgery. San Diego rookie linebacker Manti Te'o also sat out with an injured foot.