Gastroenteric infections, an important public health problem and a principal cause of morbidity and mortality in both developing and developed countries as well. Many enteric infection causing organisms have adapted to the drugs designed to kill them and this has paved the way for alternative medicine from natural origin. Allicin, an antibacterial compound in Allium species like Garlic (Allium sativum) has extensive pharmacological effects against many pathogens. This compound is also present in other Allium species such as Onion (Allium cepa L.) which is known for its high flavonoid compound quercetin. This study focuses on anti H2O2 activity and antibacterial efficacy of Onion with Garlic. Antibacterial potentials of the extracts was assessed for four bacterial isolates which include Escherichia coli, Vibrio parahaemolyticus, Salmonella typhi, Enterobacter aerogenes associated with gastroenteric infections. All the bacterial strains showed varied sensitivity against the Garlic and Onion extracts. The maximum Zone of Inhibition observed are as follows: Onion extract showed 15mm,17mm,14mm,13mm against Enterobacter aerogenes, Escherichia coli, Salmonella typhi, Vibrio parahaemolyticus whereas the Garlic showed slightly higher Zones of Inhibition as 18mm,24mm,25mm&17mm respectively. The Time Kill curve shows the maximum kill has occurred for Methanolic extracts of garlic and immature onion bulbs when compared to the aqueous extracts. The maximum free radical scavenging took place for Methanolic garlic and onion extract which showed IC50 values - 132.12μg/ml and 414.89μg/ml respectively. The findings made in this study support the use of Onion as an alternative natural remedy against gastroenteric associated infections.