Heat coals or gas grill for direct heat. In 1-quart saucepan, mix marmalade, vinegar, oil and sage. Cook over low heat about 1 minute, stirring occasionally, until well blended. Stir in chives. Reserve 1/3 cup marmalade mixture to serve with chicken.
Sprinkle chicken with garlic salt and pepper. Cover and grill chicken over medium heat 15 minutes; turn chicken. Cover and grill 20 to 30 minutes longer, turning occasionally and brushing 2 or 3 times with marmalade mixture, until juice of chicken is no longer pink when centers of thickest pieces are cut.
Serve reserved marmalade mixture with chicken.