Preheat an outdoor grill for medium heat. Cook bread slices on the grill until underside is toasted, 2 to 3 minutes. Flip bread over and baste the grilled sides with about 1/2 of the oil mixture. Grind salt and pepper on top. Grill until bottoms are toasted, 1 to 2 minutes.
Flip bread slices over once more; baste with remaining oil mixture. Season with salt and pepper and remove from heat.