Preheat a grill to medium-high. Drizzle the olive oil on the pork chops, plums and onion; season with salt and pepper. Arrange on the grill and cook, turning once, until the plums and onions are softened and just charred, 6 to 8 minutes, and the pork chops are golden-brown and cooked through, 10 to 12 minutes. Transfer the plums and onion to a medium bowl and cover tightly with foil; let stand for 10 minutes.
Coarsely chop the plums and onions and return to the bowl. Stir in the lemon juice, ginger and vinegar; season with salt and pepper. Spoon over the pork chops.