Preheat oven to 375 degrees. Coat a 9” oven proof pie plate, oven proof dish or 2 smaller oven proof dishes with cooking spray.
In a small nonstick pan, heat the oil. Add the garlic and onions and saute until soft, about 2 minutes.
In medium bowl, add the cooked onions, ¼ cup cheese, ranch dressing, spinach, artichoke hearts, pepper and mix until well blended.
Transfer to baking dish. Bake for 20 minutes. Remove from oven and sprinkle top with 2 tablespoons Parmesan cheese. If baking in two dishes, sprinkle each with 1 tablespoon cheese. Bake for 5 minutes until cheese is melted.
Store any leftovers in the fridge. Reheat before serving.