Russell Slade's men have dropped points in each of their last two games, with the London club held to draws by Bristol City and Sheffield United.
Orient remain top of League One despite those slip-ups, but will need to be at their best if they are to avoid defeat against a Bradford team unbeaten in their last five league outings.
Brentford start life after Uwe Rosler, who left the club last week to join Championship side Wigan Athletic, when they take on in-form Oldham Athletic at Griffin Park in new manager Mark Warburton's first game in charge.
Bristol City can move out of the relegation zone if they beat Rotherham United in Steve Cotterill's first league game as boss, while Shaun Derry's Notts County travel to Colchester United eyeing a win that could take them off the bottom of the table.
Crewe Alexandra's porous defence will need to improve if they are to take anything from their game with free-scoring Coventry City, and fellow relegation candidates Stevenage host Port Vale hoping to avoid a third straight league defeat.
Darren Ferguson's Peterborough travel to Gillingham as they seek momentum in the promotion following the Cambridgeshire club's surprise win over Wolves.
