More than a thousand Starbucks employees went on strike on Thursday on what is one of the company’s busiest days. Members of the Starbucks Workers Union are picketing outside more than a hundred stores across the country on what they say is the group’s largest single-day strike. The walkout falls on what’s known as Red Cup Day, when the coffee giant hands out limited-edition holiday reusable cups. They’re considered collector’s items and customers line up at the crack of dawn to get their hands on a decorated cup. It’s one of the coffee giant’s most profitable days on the calendar.

Serrano says she has worked at Starbucks for about four and a half years. The store she works at is one of the 264 that have voted to unionize over the past year and joined the nationwide strike on Thursday. Staffing is just one of the issues that Starbucks Workers United representatives say prompted them to launch the so-called Red Cup rebellion: A national strike with more than 100 stores staging their own picket lines.

According to the union, the company has retaliated against union leaders, and Starbucks lawyers have walked out on bargaining sessions or made last-minute rescheduling requests that make it challenging for members to participate.
But Starbucks’ A.J. Jones, an executive vice president of communications, disputes that allegation. Jones said the company has probably been “overly aggressive” in trying to schedule bargaining sessions. The problem with recent talk breakdowns, he said, is that union leaders at the table want to record or broadcast negotiation talks on social media — a legal no-no.