Preheat oven to 375 °F or grill to medium-high heat.
In a large bowl, toss onion, zucchini, peppers and mushrooms with 2 Tablespoons olive oil and season with salt and pepper.
Spread vegetables in a single layer on baking sheet coated with cooking spray or in a grill basket and roast for 20 minutes or until the vegetables have softened and edges are browned.
On a lightly floured work surface, roll out dough into a 15-inch circle.
Brush with 1 tablespoon of the olive oil.
Lay dough onto grill, oil side down. Cover and grill over medium coals, about 3 minutes or until dough is puffed and underside is browned.
Using tongs, turn pizza over and quickly spread the top with ranch dressing.
Top with chicken, vegetables and cheese and cover with grill lid.
Grill another 2 to 3 minutes or until cheese is melted and underside of pizza is browned. Use tongs to slide onto cutting board.
Drizzle barbecue sauce on top and sprinkle and enjoy!