Asda has said it will spend £73m to cut or freeze prices on 100 products, while Morrisons says it will cut prices on 500 products.
The Morrisons products subject to reductions represent 6% of its total sales, and include items such as eggs, cereal, cooking sauces, chicken and sausages.
Asda said its price cuts would be on fresh fruit and vegetables, fresh meat, rice and noodles.