Kevin Lisbie notched twice in the first-half for Russell Slade's side at the Matchroom Stadium.
And it was three in the 56th minute when Dean Cox struck before Danny Haynes pulled one back for the away side. Shaun Batt and Jayden Stockley notched late in the game to complete the rout.
The result leaves Orient top of the table with 21 points, while County prop up the division having taken just one point from their first seven games.
Kenny Jackett's Wolverhampton Wanderers suffered a surprise 1-0 defeat at home to Walsall at Molineux.
After a goalless first half, Andy Butler delighted the travelling supporters in the 69th minute to leave Wolves third and move Walsall up to seventh.
Jay Emmanuel-Thomas rescued a point for Bristol City as his 84th-minute goal secured a 1-1 draw with Shrewsbury Town at Ashton Gate.
Jon Taylor put the away side ahead in the 28th minute. But Graham Turner's side were denied all three points by Emmanuel-Thomas' late intervention.
Despite the late goal, Sean O'Driscoll's side remain in the relegation zone, and are still looking for their first win on the campaign.
