1. Preheat oven to 375°F. Trim beets, leaving 1 inch of stems and roots; wash. Place beets, 2 teaspoons of the oil and 1/4 teaspoon of the pepper in large resealable plastic bag. Toss to coat beets. Place beets on shallow baking pan.
2. Roast 40 to 45 minutes or until fork tender. Cool beets. Peel and cut into 1/2-inch wedges.
3. Mix orange juice, remaining 1 tablespoon oil, vinegar, parsley, remaining 1/4 teaspoon pepper, salt and garlic powder in small bowl with wire whisk until well blended.
4. To serve, place 1 cup mixed greens on each of 4 plates. Top each with mandarin orange sections and beets. Sprinkle with walnuts and drizzle with dressing.