Preheat oven to 350 degrees F. Spread pecans on a baking sheet. Bake until toasted, about 5 minutes.
Prepare grill (medium heat) or preheat broiler. Spray pears lightly with cooking spray or brush with oil. Grill or broil pear slices until brown in spots and tender, about 2 minutes per side.
Trim and pound the boneless, skinless chicken breast to uniform thickness. Brush chicken with olive oil and season with salt and pepper. Grill over medium heat until cooked through and the juices run clear. Cool chicken and tear into bite size pieces.
Place greens in a serving bowl. Top with pecans, pears, chicken, red onion and crumbled blue cheese. Top with dressing and serve.