Heat grill or grill pan to medium-high. In a medium bowl, combine orange, avocado, onion, cilantro, lime juice, and sesame oil. Season to taste with salt and pepper and set aside.
Season salmon and bok choy with salt and pepper and drizzle with olive oil.
Grill salmon, flipping halfway through, until cooked through, 3 to 4 minutes per side. Grill bok choy until bright green and slightly wilted, about 1 minute per side. Spoon avocado salsa over fish to serve.