Slightly modified from the June 2011 Sunset Magazine:

2 tbsp soy sauce
2 tbsp Asian Chili garlic sauce
2 tbsp olive oil
3 tbsp unseasoned rice vinegar
1 tbsp sugar
2 tsp finely chopped garlic
Cut four heads of baby bok choy lengthwise, being careful to keep intact.
Brush with two-thirds of the sauce.
Wrap bok choy tops with foil.
Cook on medium grill (350 – 450 degrees) for a total of 5-6 minutes, turning once.
Bok choy should be slightly softened and streaked brown.
Remove foil and brush with remaining sauce.
Can be sprinkled with 1/4 cup chopped roasted cashews.