Heat oil in a large nonstick skillet coated with cooking spray over medium-high heat until hot. Add onion and saute till translucent.
Sprinkle salt, pepper, and thyme over the top of the chicken. Add chicken to skillet and saute 6 minutes on each side or until done. Remove chicken from skillet and keep warm. Reduce heat to medium low. Add preserves, vinegar, and salt and pepper, stirring constantly until the preserves melt. Spoon the sauce over chicken to serve.