Lightly brush the pear slices with oil; cook on the preheated grill for 10 to 15 seconds per side or just until the grill markings become light brown. Transfer to a plate.
To assemble the salads, arrange the endive and leaf lettuce on plates. Slice the chicken into thin strips; arrange atop the greens along with the pear slices. Drizzle with the vinaigrette, sprinkle with pepper, and garnish with feta cheese and hazelnuts.