In a large heavy saucepan, bring water and 1/2 teaspoon salt to a boil. Reduce heat to a gentle boil; slowly whisk in cornmeal. Cook and stir with a wooden spoon for 15-20 minutes or until polenta is thickened and pulls away cleanly from the sides of the pan. Stir in basil.
Spread into an 8-in. square baking dish coated with cooking spray. Refrigerate for 30 minutes.
Meanwhile, in a large skillet, saute the eggplant, onion and green pepper in 2 tablespoons oil until crisp-tender. Add garlic; cook 1 minute longer. Stir in the tomatoes, olives, oregano, pepper and remaining salt. Cook and stir over medium heat for 10-12 minutes or until vegetables are tender.
Cut polenta into four squares. In another large skillet, cook polenta in remaining oil in batches for 7-8 minutes on each side or until golden brown. Serve with ratatouille; garnish with basil.
Prep time does not include chilling time.