In a large skillet, heat 2 tablespoons oil over medium-high heat.
Add remaining oil, peppers, mushrooms, onion, lemon juice and 1/4 teaspoon salt.
Cook, covered, over medium heat until vegetables are tender, stirring occasionally, 6-8 minutes.
Place fish over vegetables; sprinkle with pepper and remaining salt.
Cook, covered, 2 minutes longer or until heated through. Sprinkle with chives and, if desired, pine nuts before serving.