Rapid hydrolysis methods for producing oat-based beverage compositions, and compositions produced thereby. Continuous flow process to yield a hydrolyzed oat-based beverage in only a few hours, comprising a sequential treatment of an oat flour slurry with glucoamylase and then alpha-amylase enzyme with respective hydrolysis times of less than about 1.5 hours to yield a final hydrolyzed oat slurry, and finishing the composition with one or more flavorings or additional ingredients yield the oat-based beverage composition.