Place the halves, cut side up, in a three-quart baking dish with a lid or a deep baking pan that can be covered with foil. Drizzle the artichokes, including the leaves, with two tablespoons of the olive oil. Place two garlic cloves in the cavity of each artichoke half, then sprinkle with salt and pepper. Cover the dish and bake for 40 minutes, or until the thickest part at the base of the artichokes is easily pierced with a knife.