In a large bowl, combine mushrooms, bell peppers, zucchini and red onion. Drizzle with olive oil and season with garlic powder, Italian seasoning, salt and pepper.
Grill vegetables for 10 minutes or until tender.
Remove vegetables from the grill and set aside.
Preheat oven to 425°F (220°C). Place pizza crust on a baking sheet.
Spread tomato sauce over crust and top with grilled vegetables.
Bake for 12-15 minutes or until cheese is melted and crust is golden brown.