The company has since been working with other OSI plants to restore supplies to the affected restaurants. Still, sales are likely to continue suffering given the sensitivities around food safety in China. Yum Brands, which owns KFC and Pizza Hut, says it did not rely as heavily OSI and quickly cut all ties with the company. But it has nevertheless seen sales battered as well.
McDonald's Corp., which has more than 35,000 locations around the world, warned earlier this week that the scandal puts its global sales forecast for 2014 "at risk." It had previously said it expects sales to be "relatively flat."
If the figure were to fall, that would mark the annual decline for global sales since 2002.
Back in the U.S., McDonald's has failed to boost sales since October amid intensifying competition and shifting eating habits. The drop in July came despite its sponsorship of the World Cup.
Part of the problem is that chains like Chipotle are gaining favor by touting more wholesome ingredients and the ability to customize food. McDonald's is trying to adapt on multiple fronts, including a "Build-Your-Own-Burger" test in Southern California and a new Bacon Clubhouse burger positioned as a premium offering at $5 or $6.
McDonald's CEO Don Thompson has also noted that the company's lower-income customers are struggling more financially, making them reluctant to eat out.
Thompson has also said McDonald's complicated its menu and slowed down service by introducing too many items too quickly. He says the company is working on getting the basics rights — such as improving service.
The one bright spot in July was Europe, where sales at established locations edged up 0.5 percent.
McDonald's shares edged up 4 cents to $93.35 Friday morning. Over the past year, its stock is down about 5 percent.