In 350 BC, Valerius was made praetor, a title which although inferior to the consulship in both prestige and "imperium", was sometimes held by ex consuls in this early period in the title's history. In this year, Rome was beset by a very large army of hostile Gauls, and in reaction to this, the consul Marcus Popillius Laenas levied all young Roman men he could muster, as the Romans had a very particular fear of Gauls as a result of the Gallic sack of Rome forty years prior. Popillius took four legions' worth of men with him personally to fight the Gauls as an initial force, leaving the remainder under the command of Valerius as praetor to lead as reserves in case they were needed in a later battle against the Gauls or to combat another outside threat if they attacked Rome. These reserves were not needed however, as no other foreign enemy attacked and Popillius achieved victory against the Gauls.