In small bowl, combine marmalade, tarragon and onion salt.
Remove cooking grid.
Center drip pan directly on lava rocks.
Skewer and balance hens lengthwise on spit.
With string, tie legs and wings close to body of each hen.
Rotiss hens at MEDIUM with hood closed until internal temperature reaches 185°F, about 1 hour.
Brush with glaze during last 15 minutes.
Brush again before serving.