It was also the last game on French soil for coach Didier Deschamps, who steps down following the World Cup after 14 years in charge of Les Bleus. He picked Kylian Mbappe and Ousmane Dembele in a glittering attack along with Olise and Desire Doue.
Olise netted from close range in the 43rd minute after Dembele's shot was blocked, then grabbed his second in the 49th, blasting in from near the penalty spot after the visitors failed to clear a cross from the right.
Saving the best for last, the fleet-footed winger broke off the right wing and bent an unstoppable shot into the top left corner from 20 meters in the 75th.
Olise grabbed 22 goals in all competitions for Bayern Munich this season and looks a certain World Cup starter for two-time champions France — the runners-up to Argentina four years ago — against Senegal on June 16 in New Jersey.
After Olise's second goal, France's defence went napping and Patrick Kelly tapped in a cross midway through the second half for Northern Ireland.
Mbappe failed to add to his 56 international goals and remains one behind France's all-time highest scorer Olivier Giroud.
In New York, Liverpool forward Cody Gakpo's second penalty gave the Netherlands a scrappy 2-1 win against Uzbekistan.
His first came in the 32nd minute, but poor defending allowed Fabio Cannavaro's side to level in the second minute of first-half added time through Igor Sergeev. When the Netherlands were awarded another penalty, Gakpo slotted in his 21st international goal.
Ronald Koeman's men open their campaign against Japan in Dallas on June 14.
The Dutch lost the 2010 World Cup final to Spain, who play a warm-up match against Peru in Mexico later on Monday (Tuesday AEST).
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