Heat oven to 375°F. Lightly grease a 10-inch cast iron skillet or 8" square baking pan.
Stir together milk, olive oil, egg, and cornbread mix until moistened. Stir in rosemary and grated cheese. Spoon batter into prepared pan and spread evenly.
Bake 22-25 minutes or until light golden brown. A toothpick inserted into the center should come out clean. Cool completely and store tightly wrapped.