Vernon Davis, who has been deaf since childhood, was demoted from prep cook, had his hours reduced and was finally fired, though he had performed satisfactorily since he was hired in May 2008, the lawsuit said.
A spokeswoman for McCormick & Schmick's, based in Portland, Ore., could not be reached Tuesday.
The chain has more than 80 locations across the United States, with four in Maryland, including one in Annapolis and one restaurant and an M&S Grill in Baltimore, as well as the Oxon Hill restaurant in Prince George's County.
The alleged conduct by the restaurant violates the Americans With Disabilities Act, the EEOC said. The agency said it filed the lawsuit in U.S. District Court in Greenbelt after failing to reach a pre-litigation settlement with the restaurant.