From the excellent Labraunda site I quote: “The Temple of Zeus in the western part of the Temple Terrace is oriented to the east. It had 6 Ionic columns on the front and back, and 8 columns on the flanks and measured 13.87 x 18.71 m between the corners of the stylobate. That there were only 8 columns on the long sides is unusual; a normal temple would have had between 11 and 13 columns on the flanks.. The reason for this seems to be that the temple had an earlier phase, probably dating to the end of the 6th century BC. At that time it had only two columns at the entrance on the eastern front and a square cella, measuring 6.6 m by 6.6 m on the inside. On the outside, this early temple, which is identical with the cella and pronaos in the later, peripteral temple, measured 8.04 by 11.28 meters. An Ionic capital, large dentils and some ovolo blocks have been identified as probably belonging to the early temple. In the second phase, at the mid-fourth century, when the temple was rebuilt with columns on all sides, the flanks of the temple received only 8 columns. “