Espanyol did take the lead in the 22nd minute when Colotto placed his low shot into the bottom corner past the outstretched hand of Andres.
Just before the break, Osasuna did find an equaliser when Punal lifted a cross into the box and Javier Acuna fired a low effort into the bottom corner.
After half time, Espanyol could have retaken the lead when Simao raided down the flank and crossed for Christian Stuani, but his header went wide of the target.
Stuani went close again for the home side but his header again went inches wide of the post with Andres beaten after he latched onto David Lopez's cross.
Osasuna tried to up the ante late on to steal a winner but were unable to get the goal and were forced to settle for a point in their fight against the drop.