Thread 5 scallops onto each of 6 (12-inch) skewers. Cover and chill.
Cut peppers in half lengthwise; discard seeds and membranes. Place pepper halves, skin sides up, on a foil-lined baking sheet; flatten with hand. Broil 15 minutes or until blackened. Place in a zip-top plastic bag. Seal and let stand 10 minutes. Peel peppers, and discard skins. Place peppers, broth, and wine in a blender; process until smooth. Combine pepper mixture and basil in a skillet. Bring to a boil; cook until reduced to 1 1/2 cups (about 5 minutes). Reduce heat to medium-low; gradually add butter, stirring until melted. Cover and keep warm.
Sprinkle kabobs with salt; place on grill rack coated with cooking spray. Grill 2 1/2 minutes on each side or until done. Serve with bell pepper sauce. Garnish with fresh basil, if desired.