The objective of this experiment was to suggest the optimum nitrogen fertilization level for orchardgrass(0G)- red clover(RC) mixtures. The field trials were conducted from 1993 to 1994 in order to evaluate the dry matter yield, botanical composition, chemical composition, dry matter digestibility(DMD), crude protein dry matter (CPDM) and digestible dry matter(DDM) yields on the nitrogen levels( 0, 50, 100, 150 and 300kgha). The results obtained were summarized as follows : 1. With increasing nitrogen levels, the DM yield of OG-RC mixttures significantly increased(P<0.05). The maximum total DM yield (7,964kgha) was obtained at N 300kgha level, However, there was no significant difference between N 150 and 300kgha. 2. With increasing the nitrogen levels, the botanical composition of OG in OG-RC mixttures was significantly increased(P< 0.05), whereas that of RC was remarkably decreased(P< 0.05). 3. The CP content was decreased by increasing nitrogen level(P<O.O5), but the NDF content was increased (P< 0.05). On the otherhand, there was no significant difference among nitrogen levels. 4. The total CP yield of 1,081kgha was obtained at N 150kgha level(P<0.05), but there was no significant difference between N 150 and 300kgha. With increasing nitrogen level, the DDM yield was significantly increased. When N 300kgha was applied, the DDM yield was the highest with results of 5,675kgha, However, there was no significant difference between N 150 and 300kgha level. Considering the botanical composition of the RC, DM yields and quality based on the above results, it can be suggested that the optimum nitrogen level was 150kgha in the OG-RC mixtures.