1. Preheat oven to 350°. Bring 3 cups water and 1 tsp. salt to a boil in a 2-qt. saucepan over medium-high heat. Whisk in cornmeal; reduce heat to low, and simmer, whisking constantly, 3 minutes or until thickened. Remove from heat, and stir in steak seasoning and 1/4 cup cheese. Spread cornmeal mixture into a lightly greased 11- x 7-inch baking dish.
2. Brown Italian sausage in a large nonstick skillet over medium-high heat, stirring often, 10 minutes or until meat crumbles and is no longer pink; drain and transfer to a bowl.
3. Sauté onion, bell pepper, and zucchini in hot oil in skillet over medium heat 5 minutes or until crisp-tender. Stir in sausage, tomatoes, and tomato paste; simmer, stirring often, 10 minutes. Pour sausage mixture over cornmeal crust. Sprinkle with remaining 3/4 cup cheese.
4. Bake at 350° for 30 minutes or until bubbly. Sprinkle casserole with parsley just before serving.