Sprinkle both sides of chicken with 1 teaspoon of the Spicy Montreal Steak Seasoning. Grill over medium heat 5 to 7 minutes per side or until chicken is cooked through. Cut into short thin strips. Mix tomato sauce and remaining 1 teaspoon Seasoning.
Stretch or roll dough on floured baking sheet to a 12- to 14-inch round, about 1/4-inch thick. Brush top of dough with oil. Place oiled-side down on the grill. Close lid. Grill over medium heat 1 to 2 minutes or until grill marks appear on the bottom of the crust. Carefully flip crust over using tongs or spatula.
Spread seasoned tomato sauce on crust. Layer with 1/2 of the mozzarella cheese, grilled chicken, onion, remaining mozzarella cheese and Cheddar cheese. Close lid. Grill 3 to 4 minutes longer or until cheese is melted and crust is browned. (Check pizza often to avoid burning. Rotate pizza, if necessary.) Sprinkle with blue cheese. Slide pizza onto baking sheet. Slice and serve immediately. Sprinkle with additional Spicy Montreal Steak Seasoning, if desired. Serve with celery or carrot sticks, if desired.