A three-goal salvo inside seven first-half minutes saw the hosts recover from going behind to a 30-yard drive from Stephen Gleeson which left keeper Jamie Jones stranded.
In the ninth minute the home side were back on level terms when Scott McGleish netted his 13th goal of the season.
The veteran striker collected a pass from Andrew Whing and drove his shot from the edge of the penalty area into the bottom left corner past David Martin.
Orient midfielder Dean Cox then saw his 20-yard drive strike an upright, but they took a deserved lead after 14 minutes when Cox delivered an inch-perfect cross into the penalty area for central defender Terrell Forbes to nod home.
The loss of influential midfielder Stephen Dawson just before half-time knocked the O’s out of their rhythm and their opponents dictated matters in the second-half and gained a deserved equaliser through Sean O’Hanlon. The defender met a free-kick from Peter Leven 11 minutes into the second-half to head home from close range.