The 19-year-old midfielder is set to join the Championship club on a temporary deal after struggling to break into Roberto Di Matteo's first team plans
The 19-year-old has struggled to hold down a first team berth since making his breakthrough at Stamford Bridge in 2010.
He will now spend the campaign with Tony Mowbray's side, which finished seventh in the Championship last season, just missing out on the playoffs.
The highly-rated Englishman spent half of last season away from the west London club after being loaned out to Swansea, but went on to make just four appearances for the Welsh side.
His Chelsea debut came in a 2010 Champions League clash with MSK Zilina, and he has since made 22 appearances in total for the Blues.
McEachran helped England to victory in the 2010 European Under-17 Championship and made his debut for the Under-21 side at just 17.