Place cheeses in a large mixing bowl and let stand, covered, at room temperature for 30 minutes. Add sherry or wine, mayonnaise, and Worcestershire sauce. Beat with an electric mixer until combined. Stir in the olives, parsley, and onion. Transfer to a serving bowl. Cover and chill for 2 to 24 hours.
Let mixture stand at room temperature for 1 hour before serving. Serve with baguette slices or crackers. Makes 2-1/2 cups (10 to 12 servings).