Pears are ripe when they yield to gentle pressure next to the stem. If yours aren't quite ready, let them stand at room temperature for a day or two.
In a large bowl, whisk together vinegar, oil and 1/4 tsp. eachsalt and pepper. Add endives, parsley and pears; toss to coat in dressing. Arrange on 4 plates, top with pecans and a slice of blue cheese and serve.