In a medium saucepan, cook rice mix and onion according to package directions for the rice. Cool completely. Transfer to a large bowl; mix in turkey and the cranberries or raisins.
Trim heavy center vein from each cabbage leaf. In a large amount of boiling water cook cabbage leaves, uncovered, for 3 to 5 minutes or until just tender. Drain well. Set aside.
Place about 1/2 cup of the turkey mixture in the center of a cabbage leaf. Fold over both sides and roll up; secure with a toothpick, if necessary. Repeat with remaining leaves and turkey mixture. (Place the rolls in a covered storage container and chill for up to 24 hours, if desired.)
To serve, in a 12-inch skillet stir together soup or gravy and yogurt. Arrange the cabbage rolls, seam-side down, in the yogurt mixture. Bring to boiling; reduce heat. Cover and cook over low heat for 20 to 25 minutes or until no pink remains in filling. Spoon sauce onto serving plates. Set rolls atop. Makes 4 servings.