Hombre, se suele invitar a los intérpretes nominados, por lo que entiendo que los ganadores son también invitados y Mo,Nique, nos guste o no, ganó un Oscar. Pongo los requisitos de los intérpretes para poder ser invitados:
To be considered for invitation to membership in the Actors Branch of the Academy, an individual must:
(a) have a minimum of three theatrical feature film credits, in all of which the roles played were scripted roles, one of which was released in the past five years, and all of which are of a caliber that reflect the high standards of the Academy,
and/or
(b) have been nominated for an Academy Award in one of the acting categories,
or
(c) have, in the judgment of the Actors Branch Executive Committee, otherwise achieved unique distinction, earned special merit or made an outstanding contribution as a motion picture actor.
http://www.oscars.org/academy/member...ts/actors.html
Con estos requisitos vemos que puede entrar casi cualquier intérprete que trabaje más o menos de forma continuada. Saludos