Heat a large nonstick skillet coated with cooking spray over medium heat. Add onion and garlic; sauté 3 minutes or until tender. Add spinach, and cook 1 minute.
Turn heat to low; add cream cheese and next 5 ingredients. Stir well; remove from heat.
Preheat oven to 350°.
Divide spinach mixture among fish fillets, spreading evenly over each and leaving a 1/4-inch margin around edges.
Roll up each fillet, jelly-roll fashion, starting with the tail end, and secure with wooden picks.
Place fish in a 13 x 9-inch baking dish coated with cooking spray. Bake at 350° for 20 to 22 minutes or until fish flakes easily when tested with a fork. Serve immediately.