Preheat oven to 425 degrees F. Lightly oil a 16-inch round pizza pan with olive oil. Stretch pizza dough to fit in the pan.
In a small bowl mix together the Ranch dressing and minced garlic. Spread mixture evenly on the crust.
Evenly sprinkle half of the mozzarella cheese and all of the cheddar cheese over the sauce. Then spread the chicken, tomatoes and green onion over the cheese. Top with the remaining cheese.
Bake for 13-15 minutes, or until pizza dough is golden brown and cheese is melted and bubbly. Remove from oven and let stand for 5 minutes. Slice and serve. Enjoy!