Prepare two 9x13 casserole dishes with nonstick cooking spray.
In a large skillet over medium heat, add 1 tablespoon of olive oil and brown the sausage in batches.
Meanwhile, toss together the onion, bell peppers, and green beans. Drizzle with several tablespoons of olive oil and season with salt and pepper. Divide evenly between the two casserole dishes.
Divide the sausage between the two casserole dishes and mix in with vegetables.
In a medium bowl, stir together diced tomatoes, garlic, basil, oregano, salt and pepper. Pour over the casseroles.
Cover the casserole dishes with aluminum foil and freeze.
When ready to cook, preheat the oven to 350 degrees. Bake the casseroles for 1 hour, covered.