Cook quinoa per package directions and set aside when cooked.
Preheat oven to 375°F and prepare a baking sheet with foil and spray with nonstick cooking spray.
Season fish with 1/2 teaspoon salt and 1/4 teaspoon pepper, then brush 1 tablespoon nonfat Greek yogurt on each fillet.
Mix panko breadcrumbs and chopped pistachios with 1 tablespoon olive oil; sprinkle over fish, pressing gently to adhere. Bake until opaque throughout, 12 to 15 minutes.
While fish is baking, fluff quinoa with a fork, then add baby spinach, lemon juice, 1 tablespoon oil, and 1/4 teaspoon each salt and pepper; toss to combine and serve with fish.