Onion-Cheese Bisque

2 to 3 cups chopped sweet Spanish onion
3 tablespoons butter or margarine
3 tablespoons flour
1 teaspoon salt
1/4 teaspoon pepper
1/2 teaspoon sage
4 cups milk
1 1/2 cups grated Cheddar cheese
1/2 teaspoon Worcestershire sauce
Parsley (for garnish)

In large saucepan saut