Preheat oven to 375°. While the oven preheats, combine the orange zest, juice, rosemary, oil, salt, pepper and garlic in a small bowl to form a paste. Use your fingers to separate the skin from the breast. With a spoon, stuff the paste under the skin (about 1 tablespoon per breast). Spread the remaining paste all over the top of the skin and on the backside of the breasts. Lay the 4 breasts on a parchment lined baking sheet and bake for about 30 minutes, or until the internal temperature reaches 165°.