Combine first 4 ingredients in a shallow dish. Add chicken, turning to coat. Cover and marinate in refrigerator 1 to 8 hours, turning chicken occasionally. Place drip tray on toaster oven pan. Remove chicken from dish; discard marinade. Place chicken on drip tray; broil 10 minutes on each side or until chicken is done. Divide chicken, lettuce, and salsa evenly between tortillas; roll up. Garnish with onions and oregano, if desired.