In a large pot, heat 3 tablespoons of olive oil over medium heat. Add the diced onions, carrots, and celery. Cook for about 5-7 minutes until the vegetables are tender and the onions are translucent. Stir in the minced garlic and cook for another minute until fragrant.
Stir in the tomato paste, dried thyme, oregano, salt, pepper, and Italian seasoning. Cook for 2-3 minutes, allowing the spices to bloom and coat the vegetables.
Add the fire-roasted diced tomatoes, vegetable stock, and bay leaves to the pot. Bring the mixture to a boil, then reduce the heat and let it simmer for about 10 minutes.
Add the tri-colored quinoa, Great Northern beans, frozen corn, and frozen peas. Stir well and let the soup simmer for an additional 15-20 minutes, or until the quinoa is cooked through and tender.
Remove the bay leaves and stir in the chopped baby spinach. Cook for another 2-3 minutes until the spinach is wilted. Squeeze in the juice of one lemon for brightness and flavor.
Ladle the soup into bowls and drizzle with the remaining tablespoon of olive oil. If desired, sprinkle with fresh parsley and grated Parmesan cheese before serving.
