The Blanco Cosmology Survey is a four-band (griz) optical-imaging survey of ~80deg^2^ of the southern sky. The survey consists of two fields centered approximately at (RA,DE)=(23h,-55{deg}) and (5h30m,-53{deg}) with imaging sufficient for the detection of L_ galaxies at redshift z<=1. In this paper, we present our reduction of the survey data and describe a new technique for the separation of stars and galaxies. We search the calibrated source catalogs for galaxy clusters at z<=0.75 by identifying spatial over-densities of red-sequence galaxies and report the coordinates, redshifts, and optical richnesses, {lambda}, for 764 galaxy clusters at z85% of which are new discoveries, has a median redshift of z=0.52 and median richness {lambda}(0.4L_)=16.4.

Cone search capability for table J/ApJS/216/20/table3 (Summary information for BCS data presented in this work)

Cone search capability for table J/ApJS/216/20/table5 (Optically-selected Galaxy Clusters located in the 23h BCS field)

Cone search capability for table J/ApJS/216/20/table6 (Optically-selected Galaxy Clusters located in the 5h BCS field)