The 24-year-old, former England U-21 shot stopper has fallen down the pecking order at Upton Park after arrival of experienced ‘keepers Roy Carroll and Shaka Hislop.
Stephen has made 67 senior appearances since making his debut against Bradford City in February 2000 and has made the decision to gain some valuable first team experience this season.
He spoke to the Stellar Group website and said, “The prospect of playing under Micky Adams in a new 32,000-seater stadium at Coventry was too good to turn down.