1. Preheat oven to 350°. Scrub beets and trim tops to 1 in. Spritz beets with cooking spray; place in an ungreased 8-in.-square baking dish. Bake, covered, 60-70 minutes or until tender. Cool.
2. In a small bowl, whisk vinegar, orange juice concentrate, mustard, thyme and pepper. Gradually whisk in canola and sesame oils until blended.
3. Peel beets and cut into 1/2-in. cubes. In a large bowl, combine greens, mandarin oranges and beets. Just before serving, drizzle with dressing and toss to coat. Yield: 4 servings.