DePalma’s”Greeting” and Polanski’s “ Rosemary’s Baby” we’re earlier. “Midnight Cowboy” was the first X rated film to recieve a Best Picture Academy Award.
I don’t think Greetings was a studio pix - I think it was an independent. As far as I know, Rosemary’s Baby was never an X-rated movie although, undoubtedly given the infamous “C” by the Legion of Decency.