Chicago fast food stalwart Portillo's announced Tuesday its CEO has resigned, effective immediately.

Michael Osanloo served as the president and CEO of Portillo's until Tuesday morning. He also resigned as a member of the Board of Directors.

"Leading Portillo's has been one of the great honors of my career. I am so thankful to my leadership team and all our team members whose hard work and heart make this brand iconic. Together, we achieved so much, and I will always carry immense pride in having been part of the Portillo's family," Osanloo said in a statement released by the company.

Chairman of the Board Michael Miles, Jr. has been appointed as interim CEO, the company announced. Osanloo will serve as a special advisor to Miles and the company for 90 days to support the leadership change, according to a news release.

Miles previously served as Portillo's interim CEO from 2014 to 2015 and has been Chairman of the Board at Portillo's since 2014. He previously served as president and COO of Staples and COO of Pizza Hut.

A search is now underway for Portillo's next permanent CEO.

The company recently announced changes to its strategy to achieve its growth and development plans, which included ending a Chicago pilot program testing a breakfast menu. 

The company has 90 restaurants in 10 states.