Tall Fescue (Festuca arundiacea Schreb.) is a cool season perennial grass that is adapted to a wide range of growing regions and an important forage for the livestock industry.  Tall fescue is often infected with a fungal endophyte from the genus Neotyphodium, of which the symbiosis between the fungus and plant can be beneficial resulting in drought and pest resistance.  A collection of 88 tall fescue lines from 15 different sites on the mainland of Greece and the island of Crete has been characterized based on persistence, morphological characteristics, and endophyte infection status.  The population was planted in  sward plots (5’ x 5’) using a randomized complete block design with two replications at the Red River Farm (Burneyville, Oklahoma) in October 2008.  After two years of evaluation, stand persistence of the lines varied from 0-96 %, and variability of heading date and other morphological characteristics were noted.  Chloroplast specific molecular markers classified 43 lines as Mediterranean morphotypes and the rest as Continental.  Persistence within Mediterranean and Continental lines were similar across years, with only an 8 and 7 % decrease in stands, respectively.  An endophyte-specific PCR screening protocol identified 38 lines as endophyte positive (E+).  Endophyte colonization patterns further confirmed the morphotype classifications.  The population with the greatest persistence has a mixed infection status containing both E+ and E- plants.  Persistent Mediterranean and Continental lines with superior performance will be incorporated into the Noble Foundation cool season grass-breeding program.