Gather all the ingredients listed above.
Wash and dice the onion, carrots, celery, zucchini, and red bell pepper into small, even pieces. Chop the spinach into smaller bits.
In a large pot, heat the olive oil over medium heat. Add the diced onion and sauté for 3-4 minutes until translucent. Stir in the minced garlic, carrots, and celery, and cook for another 5 minutes.
Add the zucchini, red bell pepper, dried thyme, oregano, salt, and black pepper. Cook for an additional 3-4 minutes. Pour in the vegetable broth and bring to a boil. Add the orzo pasta and diced tomatoes.
Reduce heat to a simmer and let the soup cook for 10-12 minutes, stirring occasionally.
Once the orzo is tender, stir in the chopped spinach and lemon juice. Cook for an additional 2 minutes until the spinach wilts.