Coat a Dutch oven with cooking spray; add oil. Place over medium-high heat until hot. Add onion and next 4 ingredients, and cook, stirring constantly, 5 minutes. Add wine and tomato. Bring to a boil; reduce heat, and simmer, uncovered, 5 minutes.
Add shrimp and halibut to Dutch oven. Cover and simmer 5 additional minutes or until shrimp turn pink and fish flakes easily when tested with a fork.