Cincinnati won for the third time in four weeks, while the Colts, at 1-3, finished with their 12th consecutive non-winning preseason.
The game was marred by a fan who was injured at halftime. Colts chief operating officer Pete Ward said a woman was hit by falling debris when the retractable roof opened. Ward said she walked to a nearby first-aid station.
But with both teams' biggest stars sitting out, the game was devoid of excitement.
Indy got inside the Cincinnati 10-yard line three times in the second half, but got only two field goals from Adam Vinatieri - before Obarski won it.
Copyright 2015 by The Associated Press