Can't help with your query sorry but on the occasions I have been to Olu I have never seen a supermarket , only small shops selling basic groceries . I may well be wrong as I wasn't actually looking for one . There are bigger supermarkets in Hisonaru and Fethiye though so you may get them there . I am sure someone with more knowledge will come along and help soon
Lally

just up the hill in hisaronu you have two super markets migros and azda's not sure if they do wheat free or g/f foods but you can check on the migros web site
http://www.migros.com.tr/en/marked_goods.asp
the stores you want are in mulga, fethiye /hisaronu

0 252 612 51 51 0 252 612 39 00
Fax : 0 252 612 38 18
Address : Mustafa Kemal Bulvarı.No: 4 / FETHİYE

MİGROS HİSARÖNÜ
Phone : 0.252 616 72 30-31
Address : Ata cad. Nicholas Çarşısı B Blok No:24 Hisarönü-Fethiye/MUĞLA

Thank you guys.