Preheat oven to 375°F. Spray 10-inch baking dish with nonstick vegetable oil. Place halibut in baking dish. Sprinkle lemon juice over halibut and season with salt and pepper.
Heat oil in medium nonstick skillet over medium-high heat. Add onion, mushrooms and bell pepper and sauté until crisp-tender, about 6 minutes. Add olives and paprika and stir until fragrant, about 1 minute. Season to taste with salt and pepper.
Spread vegetable mixture over halibut. Bake uncovered until halibut is cooked through, about 20 minutes.
