What kind of live oak do you have? If it's southern live oak (Quercus virginiana), the leaves are naturally pretty large. Other live oaks have smaller leaves. Any bonsai will develop smaller leaves as develops more branches (ramifies). Oaks are kind of hard to get to ramify but it can be done.
Also, it would help to put your general location in your profile. You'll get better advice if people know where you live.