The actress, now 53, couldn't believe the audacity of casting directors who had thought she would be a better fit as the grandma instead of the role as a mum.
"I had heard that at 40, everything changed," Moss shared as she discussed ageing in Hollywood with her friend and filmmaker Justine Bateman at a conversation for New York's 92nd Street Y venue.
"I didn't believe in that because I don't believe in just jumping on a thought system that I don't really align with. But literally the day after my 40th birthday, I was reading a script that had come to me and I was talking to my manager about it."
"She was like, 'Oh, no, no, no, it's not that role [you're reading for], it's the grandmother.' I may be exaggerating a bit, but it happened overnight. I went from being a girl to the mother to beyond the mother."
Moss admits the sudden change in how she was viewed in Hollywood was tough to accept, particularly as male actors rarely have to face such scrutiny over their age or looks, but she is trying to let go of her insecurities to emulate the attitudes of her European peers.
"I would look at these French and European actresses and they just had something about them that felt so confident in their own skin," she said. "I couldn't wait to be that. I strive for that. It's not easy being in this business. There's a lot of external pressure."
According to The Hollywood Reporter, the conversation between Moss and her old pal was held to promote the former actress-turned-author and director Bateman's new book, "Face: One Square Foot of Skin", which examines how society responds to women as they age.