Preheat the oven to 350°F. Grease a 9 × 13 × 2-inch baking dish.
In a large skillet, cook the bacon until slightly crisp, then cut it into smaller pieces. Remove the bacon and sauté the garlic, onion, and bell pepper in the bacon drippings until tender. Add the tomatoes, olives, oregano, bacon, and the cooked beef. Simmer this mixture, uncovered, for 10 minutes. Place half of the spaghetti in the prepared pan. Top the spaghetti with half of the vegetable-beef mixture. Sprinkle this layer with 1 cup of cheese blend. Repeat the layers. Mix the canned soup and water until smooth, and pour over the casserole. Sprinkle the top with Parmesan cheese. Bake, uncovered, for 30 to 35 minutes, or until heated through.