Make the marinade: In a medium bowl, whisk together the lime juice, mustard, salt, and pepper. While whisking, slowly stream in the oil until emulsified, then whisk in the garlic.
Place the fish in a resealable bag. Pour the marinade into the bag, turning to coat the fish evenly. Refrigerate for 1 hour.
When ready to cook, set the Traeger temperature to 400℉ and preheat with the lid closed for 15 minutes.
Remove the fish from the marinade and pat dry with paper towels. Discard the marinade. Season the fish generously on both sides with Traeger Veggie Rub.
Arrange the fish directly on the grill grates. Close the lid and cook until the fish is opaque and flakes easily when nudged with a fork, 10-15 minutes (no need to flip the fish). During the last 5 minutes of cooking, place the corn tortillas on the grill to warm.
Transfer the fish to a cutting board and cut into bite-sized pieces.
Arrange the fish, warm tortillas, cabbage, red onion, cilantro, pickled jalapeño, avocado, pico de gallo, sour cream, and lime wedges on a large platter. Serve immediately. Enjoy!
Meanwhile, warm the tortillas on the Traeger for about 5 minutes. Arrange the fish, tortillas and suggested accompaniments on a large platter. Garnish with the reserved lime wedges. Serve immediately.
