Thaw halibut and pat dry.
In a small bowl, combine orange juice, lime juice, garlic powder, onion powder, salt, & pepper.
Add halibut to a ziploc bag and pour orange juice marinade over. Allow it to marinade for 25-40 minutes.
Preheat the grill to medium-high heat.
Place the halibut on foil and grill the halibut for 10-12 minutes with a second piece of foil on top.
While the halibut cooks, add the avocado slaw ingredients (everything but the cabbage) to a blender or food processor and blend until smooth.
Toss the avocado sauce with the cabbage until well covered. Save any extra to dress the tacos.
Once the halibut is cooked, assemble the tacos on lightly toasted tortillas and add toppings.
Enjoy!