For the dressing: In a small bowl, whisk together the vinegar, olive oil, orange zest, honey, salt, and pepper. Set aside.
For the salad: Spray the grill rack with nonstick, nonflammable cooking spray. Preheat the grill to medium-high heat.
Grill the radicchio until browned, about 2 minutes per side. Cool completely.
Chop the grilled radicchio into bite-size pieces. In a medium bowl, combine the chopped radicchio, orange sections, and walnuts. Add the dressing, and toss gently to coat. Add salt and pepper, to taste, if needed. Serve at room temperature.
Recipe courtesy of Paula Deen