The 'Beetlejuice Beetlejuice' actress, 52, starred with the two now-reformed Hollywood hellraisers waged 16 in a movie called '1969'.
She told Esquire about their wild antics on set: "I don't think I'm spilling any secrets: they were obviously wasted.
"To me, they were hilarious. It wasn't, like, dark. Or maybe it was to them, but to me it was fun."
Robert, 59, and Kiefer, 57, whose drink and drug abuse are well-documented, were five years older than Winona at the time, but she insisted their "scoundrel behaviour" did not involve including her as she was treated like "the little sister".
She also said about how she stayed away from wild living until her late-20s: "Back then it was like acid and weed. I mean, you heard about cocaine, but I was never offered it until way later.
"I sort of weirdly rebelled against all that. Honestly, I didn't do anything until I was like 28.
"I was just not into partying at all. Also, in my mind, I couldn't have worked high, or drunk.
"(The thought of it) made me very nervous."
Winona added she found her high from mixing with older filmmakers and actors she worshipped.
She said one of her "mentors" in the early days of her career was Jason Robards, 78, and said she also hung about with his fellow veteran actor Roddy McDowall, then in his sixties.
Winona added: "He would have these dinner parties and invite me. It was, like, Elizabeth Taylor, Karl Malden, Jessica Tandy, Sidney Poitier. It was insane... that was my drugs. Getting to talk to them."