Heat coals or gas grill for direct heat. Cut four 18x12-inch sheets of heavy-duty aluminum foil. Place sausage, squash and bell pepper on each foil sheet. Sprinkle with onions.
Mix syrup, orange juice and salt in small bowl; pour over sausage mixture on foil sheets. Fold foil over sausage mixture so edges meet. Seal edges, making tight 1/2-inch fold; fold again. Allow space on sides for circulation and expansion.
Cover and grill packets 4 to 6 inches from medium heat 35 to 40 minutes or until sausage is thoroughly heated and squash is tender. Place packets on plates; unfold foil.