BRENTFORD slumped to their second defeat in a row to hammer the final nail into their play-off hopes.
First-half goals from Kevin Lisbie and Jimmy Smith were the difference between the sides as the Bees suffered a miserable afternoon at Brisbane Road.
The hosts had a goal disallowed inside the opening 10 minutes when Smith's effort was chalked off by the linesman's flag after Dean Cox's effort came back off the post.
However, it was the Bees who should've taken the lead minutes later when Paul Rachubka spilled Niall McGinn's cross, only for Saido Berahino to steer the rebound wide with the goal gaping.
Adam Forshaw curled a free-kick inches wide, while Leon Legge headed straight at Rachubka as Bees pressed.
But it was Orient who broke the deadlock on the half-hour mark when Lisbie glanced home Dean Cox's free-kick.
The visitors came close to levelling almost immediately, but Rachubka scrambled across his goal to keep out McGinn's header at the back stick.
However, Brentford were dealt a sucker punch on the stroke of half-time as Smith found himself completely unmarked in the box before slotting the ball past Simon Moore.
Rosler rang the changes at the break, with Harry Forrester and Antonio German replacing McGinn and Berahino.
But the Bees failed to carve out any clear-cut chances as they slipped to their second successive defeat.
BEES: Moore, Logan, Legge (Osborne 67), Dean, Bidwell, Diagouraga, Douglas, Forshaw, McGinn (Forrester 46), Donaldson, Berahino (German 46).
Subs (not used): Lee, Thompson.
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