. Combine first 4 ingredients in a small bowl; stir well with a whisk. Coat grill rack with cooking spray. Place radicchio, cut sides up, on grill rack; brush with vinaigrette. Grill 3 minutes on each side or until slightly blackened, brushing with vinaigrette after turning. Place radicchio halves, cut sides up, on plates; top with Gorgonzola cheese.