1. Heat the olive oil in a large, nonstick skillet. Add the fennel, and give it a sprinkle of salt and pepper. Saute till the fennel is browning lightly and soft (about 8-10 minutes).
2. Add the lentils, and heat them through (about 2 minutes). Add a few tablespoons of water or vegetable broth, and then add the greens. Cover them with a lid and allow them to wilt down. Then stir them around in the pan until they're cooked through. Season to taste with salt and pepper. Feel free to add any herbs you like (thyme, rosemary, parsley, etc.).
3. Divide the skillet contents onto two plates. Sprinkle each with half of the orange, and serve. A little avocado would make a great topper, too!