1. Preheat oven to 400°F. Heat oil in skillet set over medium heat; cook spinach for 3 to 5 minutes or until wilted. Let cool and squeeze out any excess moisture.
2. Meanwhile, in large bowl, whisk together flour, baking powder, sugar, Italian seasoning and salt; set aside. In separate bowl, whisk milk with egg. Whisk in melted butter; stir into flour mixture just moistened. Fold in bacon, spinach and Asiago cheese. Divide batter evenly among 12 paper-lined muffin cups.
3. Bake for 15 to 20 minutes or until muffins are golden brown and tops spring back when pressed lightly. Let cool slightly in pan on rack. Serve muffins warm or at room temperature.
4. Make-ahead: Make muffins ahead; in the morning, reheat in microwave or serve at room temperature.
Tip: Add finely chopped sun-dried tomatoes or black olives for a Mediterranean twist.