1. Preheat oven to 350°. Bake walnuts in a single layer in a shallow pan 6 to 8 minutes or until toasted and fragrant, stirring halfway through.
2. Remove and discard outer leaves of endive. Rinse endive with cold water, and pat dry. Cut each endive head diagonally into 1/4-inch-thick slices, and place in a serving bowl. Add walnuts, parsley leaves, and desired amount of dressing; gently toss to coat. Top with grapefruit. Serve with any remaining dressing.
Note: Total time includes vinaigrette preparation.