In a large skillet, heat oil over medium high heat. Stir in onions and cook for 1 minute. Add the garlic and cook for 30 seconds. Stir in the vinegar and raisins and cook for 2 minutes. Remove the skillet from the heat and add the greens and toss to coat. Immediately transfer the greens to a large bowl and add the orange and bacon. Season with salt and pepper and serve immediately.