Heat grill or grill pan to high heat. Be sure the grill is clean and lightly greased.
In a large bowl, whisk together the first 6 ingredients. Season with sea salt and black pepper, to taste.
Add the scallops, bell pepper, zucchini and scallions. Lightly toss to evenly coat.
Thread scallops, bell pepper, zucchini and scallions alternately on each of the skewers. Be sure the scallops and zucchini round's flat sides are perpendicular to the skewer. Brush any of the remaining herb mixture on.
Turn the heat of the grill down to medium-high. Place the skewers on the grill at an angle so you will get diagonal grill marks. Grill for 3 to 4 minutes on each side, until scallops are barely opaque in the middle and the edges or the scallops and the veggies are lightly charred. Transfer skewers to a platter.
Serve immediately. Top with green tahini, or serve alongside.
Notes
Cut scallops in half if over 1 inch in diameter.If using wooden skewers, be sure to soak in hot water for at least 30 minutes prior, so they don't flare up.