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.