Soak mesquite chips in water at least 30 minutes; drain.
Rinse turkey breast thoroughly under cold water, and pat dry with paper towels. Rub Mexican Seasoning Blend inside and outside turkey breast.
Preheat gas grill to medium-hot (350° to 400°) using both burners. After preheating, turn left burner off. Place mesquite chips in a disposable aluminum foil pan or an aluminum foil packet poked with holes on grill over right burner. Coat grill rack with cooking spray; place on grill over medium-hot coals.
Insert meat thermometer into thickest part of turkey, making sure it does not touch bone. Place turkey on rack over left burner. Cook, covered, 3 hours or until meat thermometer registers 170°. Let stand 20 minutes before carving.