In a gallon zip-lock bag, add salt, sugar, peppercorns, garlic, thyme and bay leaf. Add turkey breast and enough water to cover. Zip bag closed and shake 3 - 4 times to mix. Place in refrigerator and brine overnight. Next a.m., remove turkey from brine, rinse turkey well. Discard brine. Sprinkle turkey with mesquite seasoning and place in crockpot. Cover turkey with Italian dressing. Cook on low about 5-6 hours or until tender. Remove turkey from crockpot and cool. Slice turkey.