Rinse 4 boned, skinned chicken breast halves (5 to 6 oz. each); pat dry. Sprinkle both sides lightly with salt and pepper. Place halves between sheets of plastic wrap; with a mallet or a rolling pin, gently pound chicken to an even 1/4 inch thick. Peel off wrap.
Put about 1/2 cup all-purpose flour in a shallow container. Turn each piece of chicken in flour to coat lightly.
Set a 10- to 12-inch nonstick pan over medium-high heat; when hot, add 2 teaspoons olive oil. Lay 2 pieces of chicken in pan; cook, turning once, until no longer pink in the center (cut to test), 4 to 6 minutes. Transfer to a platter or plates and keep warm in a 200° oven. Repeat to cook remaining chicken in 2 more teaspoons oil.