1. Line a baking sheet with parchment paper. In a small skillet, cook and stir walnuts and maple syrup over medium heat for 2 to 3 minutes or until walnuts are toasted. Transfer walnuts to prepared baking sheet; cool.
2. Place flank steak in a resealable plastic bag set in a shallow bowl. Add 1/3 cup balsamic dressing; seal the bag. Marinate in refrigerator for 30 minutes. Remove and let stand for 15 minutes at room temperature.
3. Preheat oven to 400F. Coat a large rimmed baking pan with cooking spray. In a medium bowl, toss beets with oil and salt. Place beets on prepared pan. Bake for 35 minutes or until beets are tender, stirring once halfway through.
4. Spray broiler pan with cooking spray and preheat broiler. Remove steak from bag; discard dressing. Pat steak dry with paper towel. Place steak on prepared broiler pan. Broil 4 inches from the heat for 8 minutes for medium-rare (160F), turning once halfway through. Place steak on cutting board and cover with foil; let rest for 10 minutes. Cut steak against the grain into thin slices. Set aside.
5. In a large bowl, toss together spinach and 2 Tbsp. dressing. Serve spinach mixture topped with sliced steak, oranges, beets, goat cheese, and walnuts. Drizzle with remaining 2 Tbsp. dressing.

Each serving contains: 460 calories, 29 g fat, 7 g saturated fat, 0 g trans fat, 82 mg cholesterol, 413 mg sodium, 21 g carbohydrates, 5 g fiber, 13 g sugar, 32 g protein. Daily values: 87% vitamin A, 54% vitamin C, 13% calcium, 22% iron.