In a small bowl, combine orange juice concentrate, 4 tablespoons oil, soy sauce and garlic. Pour half of the marinade into a large resealable plastic bag; add chicken. Seal bag and turn to coat; refrigerate for 2-3 hours. Cover and refrigerate remaining marinade.
Discard marinade from chicken. In a large skillet, cook chicken in remaining oil until juices run clear. Meanwhile, in a small saucepan, saute walnuts in butter until lightly browned; remove and set aside.
Set aside 1/4 cup green onions for garnish. Add remaining onions to saucepan; saute until tender. Add the marmalade, juices, honey, orange and lemon zest, salt, pepper and reserved marinade. Bring to a boil.
Reduce heat; simmer, uncovered, for 5-10 minutes or until sauce reaches desired consistency. Serve chicken over rice; top with sauce, toasted walnuts and reserved onions.