To Marinate: Pour salad dressing into a large, resealable plastic bag. Add chicken breasts, seal bag and shake to coat. Place in refrigerator for at least 1 hour or overnight (the longer you marinate, the more taste the chicken will absorb).
Preheat oven to 350 degrees F (175 degrees C).
Remove chicken from bag, discarding remaining marinade. Place chicken in a lightly greased 9x13 inch baking dish and bake at 350 degrees F (175 degrees C) for 1 hour, or until chicken is cooked through and juices run clear. Note: Turn chicken occasionally while baking.