The 40-year-old is a huge fan of the period drama and is eager to join the the fourth series of the show, which is to air later this year, reported Contactmusic.
"Gwen just wrapped 'Iron Man 3' and is so sick of blockbusters and wants to focus more on TV. She adored working on 'Glee' and told her team to get her on to 'Downton Abbey'. She's been told that creator Julian Fellowes is thrilled and is fleshing out a cameo for her," a source added.
