The auditors the firms recruited to monitor the process have given the two companies the thumbs up, but warned that the toughest tasks still lie ahead.
The Fair Labour Association said Foxconn had reduced hours by almost a third by 2013 for the hundreds of thousands working in Foxconn plants across Southern China.
Foxconn told Reuters that it would continue to cut overtime to less than nine hours a week from the current 20, even though that could raise labour costs.
The company said that it would also make it difficult to attract workers who often seek jobs with overtime so they can earn more money.
Louis Woo, special assistant to the CEO of Foxconn, said that when the company reduces overtime it needs to hire more people and implement more automation, more investment on robotic engineering. He hoped that would mean that staff would be a little more loyal to the company so it can save more costs on recruitment and retainment, he told Reuters.
The FLA found multiple violations of labour law, including extreme hours, after launching one of the largest investigations ever conducted of an American company's operations outside the United States.
The FLA said it had verified that agreed-upon changes had been instituted and that Apple was trying to hold its partner, the world's largest contract manufacturer, accountable.
But Auret van Heerden, president and CEO of the FLA, said Foxconn faces a challenge from workers' expectations.
Lots of workers came to Shenzhen to make as much money as they can in as short a period as they can, and overtime hours are very important in that calculation, he said.
Rights groups including China Labour Watch have conducted their own studies and said that Foxconn workers were still unhappy and urged other Apple suppliers to be looked at too.
The result of the changes are that workers have to complete the workload of 66 hours within 60 hours now per week. They now get lower wages but have to work much harder and they are not satisfied with the current situation, it said.