Mamie has joined the cast of Ang Lee’s star-studded new movie, “Taking Woodstock”. Lee’s ensemble cast includes Emile Hirsch, Imelda Staunton and Liev Schreiber. Pic is an adaptation of the memoir of Elliot Tiber, who played a role in helping the historic 1969 music fest unfold on his neighbor’s farm. Jonathan Groff will play Woodstock organizer Michael Lang, Hirsch will play a recently returned Vietnam vet and Eugene Levy will play Yasgur. Jeffrey Dean Morgan is set as a closeted married man having an affair with Tiber, while Paul Dano and Zoe Kazan play a hippie couple attending the concert. Dan Fogler will play a local theater troupe head, and Mamie Gummer will play Lang’s assistant. Focus Features will begin production late this month.