Prepare the grill for indirect cooking over medium-low heat (250º-300ºF).
With a sharp knife, score in a large crisscross pattern any excessive fat on the outside of the ham.
Grill the ham cut side down over indirect medium-low heat, with the lid down, for one hour.
Meanwhile, in a small pot over high heat, bring the cranberry juice, pepper jelly, and lemon juice to a boil. Continue to cook until the juice is thick, syrupy, and reduced by half, approximately 45 minutes. Remove and set aside.
Brush the glaze all over the outside of the ham. Lower the lid. Continue to glaze every 30 minutes.
Cook the ham until an instant-read thermometer inserted into the thickest part of the ham registers 160º F, approximately 1 1/2 to 2 hours more.
Remove the ham from the grill and loosely tent with aluminum foil. Allow to rest for 15 minutes. Carve and serve with any remaining glaze.