Core pears from the bottoms, leaving stems intact. Peel pears. Place on their sides in a large saucepan; add the cranberry juice, sugar and vinegar. Bring to a boil. Reduce heat; cover and simmer for 6-8 minutes or until pears are almost tender, turning once.
Remove pears with a slotted spoon; set aside. Bring poaching liquid to a boil; cook until liquid is reduced to about 1/3 cup.
Meanwhile, brush bread with butter. Place on an ungreased baking sheet. Bake at 375° for 8-10 minutes or until lightly browned.
Divide watercress among eight salad plates; top each with a pear half. Drizzle with poaching liquid. Place toast and cheese on plates. Yield: 8 servings.