In a large pot or Dutch oven, heat a drizzle of olive oil over medium heat. Add the Italian sausage and cook it until browned, breaking it up with a spoon as it cooks, about 5-7 minutes.
Once the sausage is browned, use a slotted spoon to remove it from the pot and set it aside, leaving the rendered fat in the pot.
Add the diced onion, carrots, and celery to the pot. Sauté until the vegetables are softened, about 5-6 minutes.
Stir in the minced garlic and cook for an additional 1-2 minutes until fragrant.
Add the canned diced tomatoes, chicken broth, oregano, basil, bay leaf, and the reserved sausage back into the pot. Bring the mixture to a boil.
Once boiling, reduce the heat to a simmer and add the orzo pasta. Cook for about 8-10 minutes or until the orzo is tender. Stir occasionally to prevent sticking.
Remove the bay leaf and stir in the fresh spinach until wilted, about 2 minutes.
Season the soup with salt and pepper to taste.
Serve hot, garnished with grated Parmesan cheese and chopped fresh parsley on top.
Notes
Feel free to adjust the spice level of the sausage to your preference.