Diamond Naturals has a good line of foods for all life stages,and it has no corn,wheat,or soy.Make sure to get the "Naturals" line.I feed the lamb and Rice and the Senior 8+,and my dogs do very well on it.
I personally love Innova and InnovaEVO. However, their foods arent mass market, so you wont find them at petsmart or petco. There should be pet shops in your area that carry it.