In order to investigate the interaction between the physical form of the starter based on barley grain and the time of provision of forage on the performance of Holstein dairy calves, 60 Holstein dairy Calves (body weight: 40 ± 2 kg) were used in a 70-day trial period (from 4 to 74 days of age). Each experimental treatment consisted of 15 calves (8 females and 7 males). The experiment was conducted in a complete randomised block design with a 2 × 2 factorial design including two forms of strter (mashed versus cracked) and two time of provision of forage (0 to 70 and 40 to 70 days of experiment). Experimental treatments included: 1) mashed starter with 4% wheat straw from 0 to 70 days of experiment, 2) mashed starter with 4% wheat straw from 40 to 70 days of experiment, 3) cracked starter with 4% wheat straw from 0 to 70 days of experiment, 4) cracked starter with 4 % wheat straw from 40 to 70 days of experiment. All calves were weaned at d 60 of experiment. Rumen fluid samples were collected via a stomach tube at d 35 and 70 of the study. There were no differences in starter intake among treatments during pre-weaning and post-weaning and overall period. Average daily gain (ADG) tended to be greater in cracked barley based diet compared to mashed based diets ( P = 0.06). Feed efficiency tended to be higher in calves supplemented with straw from 40 to 70 days of experiment ( P = 0.06) compared to those recived straw trough the experimental period. The final weight tended to be higher in cracked barley based starter ( P = 0.07) compared to mashed starter. No interaction was detected between the physical form of starter and time of provision of forage on the performance responces.( P 0.05) Ruminal pH and rumination time were higher in calves fed cracked barley based diets compared to mashed barley based diets. Interaction between starter physical form and the time of straw provision was significant as non-nutritional behaviors was greatest in mashed barley based diet supplemented with straw from 40 to 70 days of experient compared to other treatments ( P 0.01). Natural detergent fiber and organic matter digestibility and dry matter digestibility were higher in mashed starter ( P 0.01).In conclusion, the results indicated that cracked barley based diet with straw provision from 40 to 70 days of experiment resulted to improved performance and rumen development of dairy Holstein calves. Keywords : Holstein Calf, Starter diets, Straw, time