Grilled Halibut Steaks with Potatoes, Olives, and Onions

INGREDIENTS

1 1/2

lbs Halibut

1 lb

Cipollini onions

1/2

lbs Golf ball-size baby potatoes

bunch Oregano, fresh

Peppery greens

2 tsp

Dijon mustard

1 cup

Olives, mixed

Kosher salt and freshly ground pepper

9/16 cup

Olive oil, extra-virgin

1/4 cup

White-wine vinegar

Ciabatta or other rustic loaf