Oscar is a tall saber-toothed tiger with golden brown fur like most of his pack. His features are long but rounded, right down to his fangs which jut out diagonally. He is brown and looks to be older than even Diego, only dwarfed in age by Soto. He is also shown to be quite a fast runner, as he was shown to be capable of outstripping Zeke and Lenny while chasing after Sid and the baby.
He was doubting in Diego's abilities, because he slipped up once in bringing the baby to Soto. In a deleted scene, he told his packmates of his disapproval of Soto's plans to stay and hunt humans, instead of follow the migrating herd animals traveling south. Oscar was sent with Zeke to find Diego and warn him to hurry and bring the baby, or not to come back at all. Oscar made it with the rest of the pack to Half Peak, where he attempted to kill Manfred, but was defeated as were the others. When he and Lenny saw Soto killed, the two ran off quickly, leaving Manfred, Sid, and a wounded Diego.