Combine first 3 ingredients in a 10-inch cast-iron skillet coated with cooking spray. Combine margarine, curry powder, and ground red pepper. Add half of margarine mixture to vegetable mixture; toss lightly.
Bake, uncovered, at 450° for 15 to 20 minutes or until vegetables are tender and lightly browned, stirring occasionally. Remove vegetables from skillet; set aside, and keep warm.
Brush remaining margarine mixture over fish. Coat skillet with cooking spray; place over medium-high heat until hot. Add fish, and cook 1 minute on each side or until browned. Reduce oven temperature to 400°. Place skillet in oven, and bake, uncovered, 8 to 10 minutes or until fish flakes easily when tested with a fork. Serve with vegetable mixture.