Heat grill to high. Brush chops with oil on both sides and season with salt and pepper. Grill the chops for 2 to 3 minutes on each side or until cooked to a medium-rare doneness. Brush the orange halves with oil and season with salt and pepper. Grill oranges, cut side down, until golden brown. Remove oranges from the grill and cut each half into quarters. Place bowl of yogurt sauce in the center of a platter and arrange chops around it with the orange quarters. Garnish with chopped mint.
Orange-Mint Yogurt Sauce:
8 ounces yogurt
1/4 cup freshly squeezed orange juice
2 teaspoons finely grated orange zest
4 cloves garlic, finely chopped
2 tablespoons finely chopped fresh mint leaves
Salt and freshly ground pepper
Place the yogurt in a medium strainer lined with cheesecloth and place over a bowl. Refrigerate for at least 8 hours or overnight. Alternatively, buy thick Greek yogurt, which does not need to be drained. Scrape the drained yogurt into a clean bowl and discard the liquid that has drained. Stir in the remaining ingredients and refrigerate for 30 minutes before serving.