Sam Dalby opened the scoring on the 20th minute, before midfielder Hector Kyprianou and Eric Lopes also found the target to send the O’s into the interval with three-goal advantage.
Dalby and Lopes then added further strikes in the second half to seal an emphatic victory under the lights in E10.
After an impressive comeback to draw against Dagenham & Redbridge just over a week ago, Coach Danny Webb made three changes to the staring XI, Ruel Sotiriou, Alfie Fleming, and Teddy Stevenson were re-introduced from the start.
An early chance fell to Biggleswade when Tyler Mitchell’s pitch long goal-kick allowed Elliot Beevor to hook a shot towards the far post but Arthur Janata did well to palm the ball away from danger.
Orient grew in to the game and after ten minutes of play Eric Lopes wriggled his way in to the box before his attempted chip to the far post bounced just wide of the target.
The visitors went close again, through Beevor who capitalised on a slip and entered the box through on goal before Janata raced off his line to close down the striker and push the ball away.
As the O’s began to look comfortable, a short corner saw Charles Clayden’s cross to the near post glanced just over the bar by Toby Stevenson.
Minutes later Orient took the lead, a through ball forward released Clayden down the left wing, his first time cross found Sam Dalby in the box who poked home past Mitchell.
Hector Kyprianou doubled the lead six minutes later after he had picked up a loose ball on the edge of the box and slotted it in to the corner of the net.
Ruel Sotiriou looked to be in on goal when Dalby’s through ball from deep allowed the former to get beyond the defence but his touch gave the ‘keeper time to gather the ball before the shot.
The O’s went close again, this time through Clayden who forced himself in to the before for his shot was tipped over the bar by Mitchell.
Eric Lopes grabbed a third for the O’s after he linked up with Sotiriou and powered home a left footed effort in to the bottom corner.
Biggleswade made one change at half time when Niall Keteley was introduced and a quiet start meant Sotiriou’s dragged shot a minute shy of the hour mark was the first on the second half.
Dalby registered his second of the evening when he stole the ball inside the box and beat his defender before he stroked past Mitchell.
Almost immediately Dalby was in space inside the box again, the striker got the ball out of his feet and aimed low but his shot was matched by ‘keeper Mitchell.
The O’s stretched their lead to five when Lopes darted in to the box and powered a shot just inside the near post.
With just over a quarter of an hour left the O’s made two changes, Sotiriou and Dalby were replaced by Jaedon Phillips and Mason Hall who made his first appearance of the season after recovering from a knee injury.
Ernold Haxhiu’s skilful footwork to lose his marker allowed him to poke the ball through to Kyprianou whose touch on the ball wasn’t enough to direct it goalwards.
The O’s will now host Sholing in the Second Round, with a date to be confirmed in due course.
ORIENT: Arthur Janata, Andrew Camilo-Tayaca, Teddy Perkins, Toby Stevenson, Alfie Fleming, Eric Lopes, Ernold Haxhiu, Hector Kyprianou (Luca Carter-Henry 81), Charles Clayden, Sam Dalby (Mason Hall 74), Ruel Sotiriou (Jaedon Phillips 74)
SUBS: Sam Amedu, Brendon Shabani
GOALS: Dalby (20 & 67), Kyprianou (26), Lopes (43 &69)
BIGGLESWADE: Tyler Mitchell, Beau McMahon, Sam Paton, Phillip Alexandrou (George Fitter 74), Edi Garibovic (Niall Kateley, 45), Elliot Beevor, Luca Allison, Robbie Buchanan (Matt Fraser 66), Samuel Gibson, Harry Watson, Robert Banks
SUBS: Patrick Sinfield, Cillian Mills