Cut orange in half crosswise; remove and discard seeds. Carefully remove pulp (do not puncture bottoms of orange halves). Reserve orange cups. Coarsely chop pulp, and place in a small bowl. Add strawberries and blueberries; toss gently. Spoon fruit mixture evenly into orange cups.
Combine yogurt, orange juice concentrate, and minced mint, stirring well. Spoon yogurt mixture evenly over fruit. Garnish with mint sprigs, if desired.