In a 12-inch nonstick skillet heat oil over moderately high heat until hot but not smoking and saute chicken, skin or skinned sides down, 3 minutes, or until golden.
Turn chicken over and saute 1 minute more.
Reduce heat to moderately low and cook chicken, covered, until just cooked through, about 10 minutes.
Coarsely chop capers and in a large bowl toss chicken with any juices from skillet, capers, and vinaigrette.