Combine olive oil, red peppers, artichoke hearts, red onion and garlic seasoning in a large bowl and toss to blend; add mushrooms and toss until mushrooms are coated with oil.
7Arrange in a single layer in four 12-inch deep dish pizza pans and bake each at 450°F for 6 minutes in an impingement oven, or until golden.
8Cover and chill to hold.