Coat an unheated large nonstick skillet with nonstick cooking spray. Preheat over medium heat. Brown chicken, half at a time, in hot skillet.
In a 3-1/2- or 4-quart slow cooker, combine frozen artichoke hearts, garlic, and onion.
In a small bowl, combine broth, rosemary, lemon peel, and pepper. Pour over vegetables in slow cooker. Add browned chicken spoon some of the garlic mixture over chicken.
Cover and cook on low-heat setting for 6 to 7 hours or on high-heat setting for 3 to 3-1/2 hours.
Transfer chicken and artichokes to a serving platter, reserving cooking liquid. Cover chicken and artichokes with foil to keep warm. If using low-heat setting, turn to high-heat setting.
In a small bowl, combine cornstarch and the cold water. Stir into liquid in slow cooker. Cover and cook about 15 minutes more or until slightly thickened. Spoon sauce over chicken and artichokes. If desired, serve with lemon wedges.