1. Place oven rack in lowest position. Heat oven to 450 degrees F. Coat 14-inch pizza pan with nonstick cooking spray.
2. Stretch and pat out pizza dough onto prepared pan. Or prepare focaccia mix following package directions, omitting seasoning packet. Spread on pan; let rest as directed.
3. Spread dressing over dough, leaving 1/2-inch border around edge. Sprinkle with half of pizza cheese. Scatter chicken over top. Sprinkle with remaining pizza cheese and the Parmesan. Top with onion rings.
4. Bake on bottom rack in 450 degrees F oven for 15 to 20 minutes or until top is bubbly and bottom is nicely browned. Let stand 10 minutes before slicing.