Combine all the ingredients except the orzo and the tomato in a shallow dish. Marinate in the refrigerator for 2 to 3 hours.
In a large stove-top grill pan or in the broiler, grill the rib chops 2 to 3 minutes per side for medium rare, 4 to 5 minutes for medium to medium well. (For loin chops, grill 5 to 6 minutes for medium rare, 7 to 8 minutes for medium to medium well.)
Meanwhile, prepare the orzo according to the package instructions for 4 servings. Add the tomato, stir, and season to taste with salt. Serve hot with the chops, accompanied by the Tsatsiki.