Trim fat from the steaks and pat them dry with paper towels. Place the steaks in a zip-top plastic bag with 2 tablespoons olive oil and the walnut oil. Massage the oil into the steaks - I like to pound them a bit with my fists. Think anger management. Grind in the salt and pepper and squish them around in the bag to coat the steaks. Refrigerate for at least 2 hours.
Place zucchini, yellow squash, orange bell pepper, tomatoes, and red potatoes on a baking tray and toss them with 2 more tablespoons olive oil, garlic and herb seasoning, a pinch of sea sal and a pinch of black pepper.
Preheat grill for medium heat and lightly oil the grate.
Place the wet planks on the hot grill, close the lid, and leave them for 3 to 5 minutes, or until slightly charred on the bottom. Turn the planks over and place the steaks on one plank. Transfer the mixed vegetables from the baking tray to the other plank. Close the lid of the grill and cook to desired doneness.