Chains like McDonald’s, which has more than 14,000 locations in North America, the majority of them independently owned, have long argued that they are not liable for the behavior of employees at franchisees’ stores. (A case that may decide whether McDonald’s is a joint employer of its franchisee staff is currently before the National Labor Relations Board.)

“This is a company that has especially used the franchise model as a shield,” said Gillian Thomas, a senior staff attorney with the A.C.L.U. Women’s Rights Project. “It’s determining literally the pattern that the sauce makes on the hamburger — it has a special machine that does that. And then throws up its hands and says, we can’t be responsible for how people operating those machines behave.”

Steve Easterbrook, the chief executive of McDonald’s, responding on Monday to a letter from Senator Tammy Duckworth, Democrat of Illinois, said the company had improved and clarified its policies on harassment; printed them on posters sent to all of its restaurants; and put most franchise owners through new training. In the coming months, he said, the company will be rolling out training for front-line employees, and a complaint hotline.

The changes began late last year, a McDonald’s spokeswoman added in an email on Monday. “By strengthening our overall policy, creating interactive training, a third-party-managed anonymous hotline and importantly, listening to employees across the system, McDonald’s is sending a clear message that we are committed to creating and sustaining a culture of trust where employees feel safe, valued and respected,” she said.

Employees maintain that, despite McDonald’s assurances, not much has changed. At least one corporate store had repeat federal c laims made against it, and this year, two had multiple complaints.

Last September, hundreds of McDonald’s workers walked off the job during the lunch rush, protesting what they said was pervasive sexual harassment in the company’s restaurants. In social media posts this year, the A.C.L.U. invited more employees to report their experiences. On Tuesday, Time’s Up released a public letter to McDonald’s leadership, pledging to fight for the workers for “as long as it takes.” And another protest, with some of those who filed new E.E.O.C. claims present, took place on Tuesday afternoon, in front of McDonald’s headquarters in Chicago, two days before the company’s annual shareholder meeting.

The E.E.O.C. has the authority to investigate complaints, which can be a lengthy process. If it finds merit to a report, it can encourage the parties to resolve the charge informally, with the agency’s help; as a last resort, the E.E.O.C. can file a lawsuit. In 2012, for example, it secured a $1 million settlement from a McDonald’s franchise owner in Wisconsin that it had sued over sexual harassment.