In the bowl of a food processor or blender, puree the onion, lemon juice, oregano, paprika and garlic. With the motor running, slowly add the oil. Place the chicken in a large, resealable plastic bag and pour in the marinade. Press the air out of the bag and seal tightly. Turn the bag to distribute the marinade and refrigerate for 1 hour. Remove the chicken from the marinade and discard the extra marinade. Barbeque the chicken over direct medium heat for about 10 minutes, turning once. Ensure no trace of pink remains inside and the internal temperature is 165F. Enjoy with rice and a green salad!