Thaw turkey. remove neck and giblets. Rinse and pat dry.
Prepare brine by combining equal parts chicken stock and water. Stir in salt and sugar until dissolved. Place turkey into the pot (or what you are using), breast side down. Tuck in onion quarters, garlic, peppercorns and a couple of bay leaves. If turkey is not fully submerged top off with additional water.
Refrigerate overnight or up to 24 hours.
Remove turkey from the brine and discard brine.
Pat turkey dry with paper towels and allow to sit at room temperature for 45 minutes.
Place a pan to catch turkey juices on a rack under where the bird will be or on the bottom. Preheat smoker to 250 degrees.
Rub turkey with grapeseed or olive oil, season lightly with S&P or a dry rub. Place butter, herbs and onion in cavity of the bird.
Place turkey in smoker. Add woodchips (usually added from outside the smoker via a tube or slot. (you may wish to add additional chips as bird smokes).
Cook turkey 18-22 minutes per pound or until thermometer inserted deep in the leg area (but not touching bone) registers 155-160.
Allow turkey to rest for 20 minutes before slicing.
Note: If you wish to baste the bird with melted butter or melted butter combined with chicken stock, do so after the first hour.