Prepare and chop all vegetables and ingredients needed.
Heat a large 6-8 quart pot over medium heat and pour in the olive oil.
Add the chopped onion, carrots, celery, and garlic to the hot oil. Season generously with salt and pepper. Cook for about 4 to 6 minutes until the vegetables soften.
Pour in the vegetable broth, diced tomatoes, tomato paste, Italian seasoning, and crushed red pepper if using. Allow the mixture to come to a rolling boil.
Add the kidney beans, great northern beans, frozen green beans, and dried pasta shells to the pot. Stir well and reduce heat to simmer partially covered for 8 to 10 minutes, stirring every couple of minutes to prevent the pasta from sticking.
Stir in the sliced zucchini, spinach, and chopped parsley. Let the soup simmer for another 2 minutes.
Taste the soup and adjust salt and pepper as needed before serving warm.