This study was carried out in Kayseri Province of Turkey in the year's 2011 and 2012 for two years to determine the effects of harvest time on hay yield and quality of different bitter vetch genotypes. A total of 16 different bitter vetch (Vicia ervilia L.) lines supplied from EMRI, DATAE and ICARDA were used as the plant material of the field experiments. Experiments were carried out in randomized block design with 3 replications. Bitter vetch lines were harvested at flower-set, full-bloom and podset periods. Green herbage and hay yields, crude protein (CP), protein yield (PY), crude ash (CA), condensed tannin (CT), acid detergent fiber (ADF) and neutral detergent fiber (NDF) characteristics were investigated. Results revealed increasing ADF-NDF ratios, green herbage and hay yields and decreasing crude protein, crude ash and condensed tannin ratios with the progression of harvest time. Pod-set period was determined as the proper harvest time. The lines VE-16, VE-5, VE-1, VE-2 and VE-6 were considered as primary lines to be used in further breeding research and agricultural activities of the region with regard to hay yield and quality.