What was the average number of viewers per episode of Grey 's Anatomy during the first four seasons ?
After two seasons of airing as a lead - out to fellow ABC series " Desperate Housewives " , the network decided to move " Grey 's Anatomy " to 9:00 ET in the Thursday night time slot , dominated by "" , where the series began airing as a lead - in to " Ugly Betty " , which aired in the time slot from its first season , until the conclusion of the third in 2009 .