Wash beets and wrap in foil.
Place in 200 C (400 F) oven for about 1 hour and 30 minutes or until knife slides easily into beets.
Let stand until cool enough to handle.
Remove skin and slice thinly; set aside.
Spread greens onto platter and sprinkle with red onions then top with beets.
With a chef’s knife and using sawing motion cut skin and white pith from oranges and cut between membranes to make segments.
Sprinkle over top of greens; set aside.
Orange poppy seed dressing: In small bowl, whisk together oil, orange rind and juice, vinegar, mustard, honey, garlic and poppy seeds. (Grating rather than crushing the garlic gives it smoother texture.)
Drizzle over salad mixture and serve.