1Heat oven to 425°F. Spray shallow roasting pan with cooking spray. Place chicken in pan; arrange squash and onion around chicken.
2In small bowl, mix dressing, salt, rosemary and garlic powder. Brush chicken and vegetables with about half of the dressing mixture.
3Bake uncovered 20 minutes. Remove from oven. Stir vegetables; add sugar snap peas to pan. Brush chicken and vegetables with remaining dressing mixture.
4Return to oven; bake 20 to 25 minutes longer or until thermometer inserted in center of thickest part of breasts reads 170°F, and vegetables are tender. If desired, garnish with fresh herb sprigs.