Brush pizza crust with olive oil on the top and bottom. Start building the pizza by spreading ½ the cheese on the crust. Next mix the dressing with the field greens. Now arrange the sliced tomatoes over the cheese on the crust, followed by the dressed greens. Finally, arrange the sliced red onions and grilled chicken over the greens and top with remaining cheese. Place pizza on med-low grill and close lid. After 3-4 minutes, turn pizza 90 degrees on grill and close lid again for 3-4 minutes (grills vary, so watch closely). The pizza is done when the bottom is crispy and all ingredients are warm. The pizza can also be baked in a conventional oven at 375 degrees for 10-12 minutes.