Preheat oven to 400°F. Heat oil in a large nonstick ovenproof skillet over medium heat. Pat the chicken dry with a paper towel and place in a large ziptop plastic bag. Add the dressing mix and shake until coated.
Place the coated chicken in the hot skillet, and cook until golden brown on each side, about 3-4 minutes.
Place skillet with chicken in the oven for 10-15 minutes, depending on how thick your chicken breasts are. Wonderful served on a plate with veggies or on top of a salad-- with ranch dressing of course!