Olympiacos shot themselves in the collective foot as two own goals prevented them narrowing the gap to Super League leaders Panathinaikos.
Avraam Papadopoulos inadvertently gave opponents Giannina the lead, but goals from former Barclays Premier League forwards Matt Derbyshire and Lomana-Tresor LuaLua put Olympiacos ahead at the interval.
However, former Aston Villa defender Olof Mellberg also put through his own goal to hand the visitors a 2-2 draw.
Fourth-placed AEK Athens eased to a 3-0 home win over Kavala. Ismael Blanco's first-half penalty set them on their way and full-back Sanel Jahic and substitute Gustavo Manduca struck after the interval.
Thanassis Karagounis and Marek Saganowski fired Atromitos to a 2-1 win over Iraklis in the day's other game, Grigoris Papazacharias replying for the visitors.
