The Napoleon Dynamite star will play a medical intern named Heather, reports Zap2it.
Her previous credits include roles on Bones, True Blood and Veronica Mars.
Gaius Charles (Friday Night Lights) and Camilla Luddington (Californication) have also signed up for roles in the new season of Grey's Anatomy.
Chyler Leigh (Dr. Lexie Grey) and Kim Raver (Teddy Altman) recently left the series, with Eric Dane (Dr. Mark Sloan) also departing at the beginning of season nine.
Grey's Anatomy returns to ABC in the US on Thursday, September 27 at 9/8c. In the UK, the show airs on Sky Living.
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