Have all of the ingredients at room temperature. Preheat oven to 375°F. Generously grease a 9 x 9-inch pan.
Place cornbread mix in a large bowl. Add milk, eggs and butter or oil. Mix until blended, then mix vigorously for 30 seconds more.
Transfer into prepared baking pan. Bake until golden brown, about 25 minutes.
For cornbread muffins: Prepare batter as above. Line standard muffin pan with paper baking cups, or spray with non-stick cooking spray. Fill cups ¾ full with batter. Bake at 375°F until tops are golden brown, about 20 minutes. Makes 12 muffins.
