This study was aimed to determine the effect of varying levels of urea treatment and preservation time on chemical composition of rice straw offer for growing beef cattle. First experiment was arranged with a completely randomized design with 04 treatments and 04 replicates. The treatments were U2: rice straw + 2% urea; U3) rice straw + 3% urea; U4: rice straw + 4% urea; U5: rice straw + 5% urea. Second experiment was arranged into a completely randomized design, consisting of three treatments and three replicates (3 animals/replicate). The treatments were control (C) 0.5 kg rice bran/100 kg body weight + natural grass ad libitum; U3: 0.5 kg rice bran/100 kg body weight + 1,5 kg natural grass/100 kg BW + 3% urea treated rice straw ad libitum; U5: 0.5 kg rice bran/100 kg body weight + 1,5 kg natural grass/100 kg BW + 5% urea treated rice straw ad libitum. The results from first experiment showed that there was not influence of urea treatment on DM and ADF contents. But CP level increased as urea added in rice straw increased (p