This study was designed to assess the marginal accuracy and flexural strength of zirconium oxide based cores veneered with pressable ceramic with variable axial distances from the core to the finish line. A master stainless steel die was machine milled to simulate a prepared mandibular premolar with a 1mm thickness shoulder finish line with rounded internal angle. A total number of 40 all ceramic crowns were fabricated. Samples were divided into four groups, ten crown per group, according to the axial distances from the core to the finish line that was completed with the veneering material. Group1: zirconium oxide core fabricated according to manufacturer's instructions (control group).•Group 2 :zirconium oxide core 0.5 mm short of the finish line.•Group 3: zirconium oxide core 1mm short of the finish line.•Group 4: zirconium oxide core 1.5mm short of the finish line.Each group was divided into two subgroups of five crowns each:•Subgroup(A): samples not subjected to thermocycling.•Subgroup(B): samples subjected to thermocycling.Marginal adaptation was assessed by measuring the vertical marginal discrepancy of the crowns on the stainless steel dies without cementation, using a travelling microscope. A total of 8 single measurements were made around each specimen.