 Rhimes is the series ' most prolific writer . She often promotes the show by answering fan questions on her Twitter account . Other members of the writing staff are Vernoff , Wilding , Peter Nowalk , Stacy McKee , William Harper , <unk> Clack , Tony Phelan , Joan Rater , and Debora Cahn . From the second through seventh seasons , the writers maintained a blog entitled Grey Matter , where the writer of an episode discussed the motives behind the writing . Directors vary by episode , with Rob Corn directing most frequently , followed by Tom Verica . Horton , Edward Ornelas , and Jessica Yu have also directed a substantial number of episodes . Cast members Chandra Wilson and Kevin McKidd have both directed multiple episodes . 
