Yes, he could have. Yuan Shao had a much larger force than Cao Cao, and if he listened to his advisors, and if his sons weren't disunified he could have. Just like what happened at Guan Du. If he would have won, pretty much all of Cao's territory would fall to Shao, and just play Yuan Shao as if he were Cao Cao. Yuan Shao certainly had more lineage and authority to the land rather than Cao Cao, because of his noble name, Yuan.
袁 "Since the dawn of time every one will die,
Let the history books note my death with loyalty at heart." --Wen Tianxiang