Using a basting brush, brush fish with oil, then sprinkle with Rosemary Garlic Seasoning, and rub in.
Grill, with barbecue lid closed, over medium-high heat (or broil in oven) until cooked through, 4 minutes per side. Grill or broil buns during the last minute of cooking, if you wish.
Meanwhile, place coleslaw in a bowl. Add Big Burger Sauce and toss to mix. Add water to thin, if needed.
Place fish on bottom halves of buns, then divide coleslaw overtop. Cover with top buns, and serve.