Brush pork chops, plums, and onion with oil and sprinkle with salt and pepper. Set on grill. Cook plums and onions for about 7 minutes, until softened. Cook pork chops for about 10 minutes, flipping midway through cooking time, until pork reaches an internal temperature of 160 degrees F.
Cut plums and onions into bite sizes. Toss with lemon juice, ginger, vinegar, and salt and pepper to taste in a bowl. Serve over pork chops.