Chevrolet-powered O’Ward led the 65-lap race when he came upon traffic in the closing stages. That helped Honda driver Alex Palou close the deficit, which he eventually overcame and passed the Mexican.
The Chip Ganassi Racing driver went on to win the race by 10 seconds, shod with the softer compound tyre.
It was a demoralising end to a near-perfect weekend for O’Ward and McLaren. O’Ward took pole position ahead of his teammate Christian Lundgaard.
It came on the same weekend Oscar Piastri took pole position and the win in the Chinese Grand Prix at Shanghai International Circuit for McLaren.
Had O’Ward won, it would have been the first time since 1976 that McLaren had won a Formula 1 and IndyCar race on the same weekend.
That year, James Hunt claimed the Spanish Grand Prix at Jarama while Johnny Rutherford won at the 1.5-mile kidney bean Trenton oval.
“I hate to whine about it, but it sucks to be the leader,” said O’Ward.
“All of our Chevy affiliate teams are worthless with helping when a Chevy leader is coming up on them.
“Honda seems to work as a team very, very well because Foster was doing everything in his power to keep me behind. Palou gets right behind him, and he just lets him cruise by.
“I still think Palou would have gotten us sooner or later. Obviously that just makes it a bit more of an annoyance rather than a joy.”
O’Ward cited his tyre strategy as his only shortcoming in the race. Palou ended the race with the faster, soft compound red sidewall tyre while O’Ward and his teammate Lundgaard.
“The team did a phenomenal job in the pits. I mean, the car has been a joy to drive all weekend. In the race, as well,” said O’Ward.
“We ran a red, black, black, black race. I think it should have been a red, red, black, black or any sort of combination with two reds and two blacks.
“I think we missed it on the #5 car. We can only see why we chose that, try not to make that mistake again.”
IndyCar returns to the streets of Long Beach on April 14.
