The Gunners made 10 changes from the side which had beaten Barcelona in midweek, but lacked a cutting edge in attack before they eventually made the breakthrough when Tomas Rosicky headed in on 53 minutes.
However, Orient produced a late rally and substitute Tehoue drilled home with a minute left to earn a money-spinning replay which keeps alive the dream of a quarter-final at Manchester United.
Arsenal finally took the lead on 53 minutes Rosicky glanced home his first goal since January 2010.
Orient could have let their heads drop, but immediately went on the offensive as Alex Revell looped a header goalwards before Tehoue drilled in an equaliser with just a minute left as Brisbane Road erupted.
Source: PA
Source: PA