Abstract: Two apparent digestion trials were conducted to determine the effect of corn grain particle size on nutrient digestibility using nine Awassi ram lambs (48.3 ? 3.2 kg). They were allocated to three treatments (3 per treatment) at random within live weight. Three treatments were used in completely randomized design with three millings degrees which included: 4mm (fine), 6 mm (coarse) and (70%) coarse + whole grain (30%) (coarse+whole) of ground corn in both apparent digestion trials. Corn:alfalfa ratios were 40:60 in trial 1 and 85:15 in trial 2. Diets were offered 2.5% of body weighs as fed basis. In trial 1, corn particle size did not DM, OM and ADF digestibility (P>0.05). Moreover, rumen fluid pH and protozoa number did not change due to dietary treatments (P>0.05). Crude protein digestibility was greater for coarse than the other two dietary treatments. In trial 2, Finely grinding decreased DM and OM digestibilities (P<0.05). Acid Detergent Fibre and CP digestibilities were not altered by the treatments (P>0.05). Rumen fluid pH was lower for finely grinding (P<0.05) compared to coarse or coarse+whole. Protozoa number also numerically decreased with finely grinding. As a result, there was no advantage of feeding finely ground corn compared with the coarsely ground or coarse+whole corn on nutrient digestibility and ruminal parameters.