When grilling, turn as soon as the outer surface which is touching the bottom of the pan become golden brown. The object is to have a grill effect on the zucchini without overcooking each spear. The outside should be browned at the points where the grill ridges were and still be a bit al dente in the middle of the zucchini.
The grilled zucchini goes well with many meat dishes or with white fish, or if serving a vegan/vegetarian meal, with tofu fried in roasted sesame oil. Enjoy!