Katheryn Rossetter, 66, played opposite Hoffman in a stage revival of Death of a Salesman in 1984, which is when she alleges the sexual misconduct took place.
"One night in Chicago, I felt his hand up under my slip on the inside of my thighs. I was completely surprised and tried to bat him away while watching the stage for my cues," Rossetter said of one incident.
"After the show he was busy with the producer and director so I had no access to him to address it. It then happened almost every show. Six to eight shows a week. I couldn't speak to him in the moment because I was on a live mic. He kept it up and got more and more aggressive. One night he actually started to stick his fingers inside me," she added.
Last Week Tonight host John Oliver recently took advantage of an opportunity to grill Hoffman over the sexual harassment allegations against him.
The two men were attending a Q&A discussion panel at an event celebrating the 20th anniversary of Hoffman's film Wag the Dog and, according to PEOPLE, Oliver turned to Hoffman and said, "This is something we're going to have to talk about because... it's hanging in the air."
"It's hanging in the air? From a few things you've read you've made an incredible assumption about me," Hoffman responded, sarcastically adding, "You've made the case better than anyone else can. I'm guilty."
Before the panel ended, Oliver addressed the other members and the audience saying, "I can't leave certain things unaddressed. The easy way is not to bring anything up. Unfortunately that leaves me at home later at night hating myself. 'Why the...didn't I say something? No one stands up to powerful men.' "
"Am I the powerful man?" Hoffman asked, before firing back, "You weren't there."
Oliver quipped, "I'm glad [I wasn't]."