Cook pasta according to package directions. adding asparagus the last two minutes of cooking. Drain; rinse with cold water. Drain; transfer pasta and asparagus to large serving bowl.
Add green onions, mint, and feta cheese to pasta mixture. Using a serrated knife, remove peel and white pith from two of the oranges. Halve oranges lengthwise, then slice crosswise. Add to pasta mixture.
For dressing, from the remaining orange finely shred 2 teaspoons peel. In a screw-top jar squeeze 2 tablespoons orange juice. Add orange peel, olive oil, vinegar, salt, and pepper. Cover and shake well. Pour over pasta mixture; toss to combine. Cover and refrigerate for 1 hour or overnight. Toss before serving. Makes 10 to 12 servings.