In a large pot, heat the olive oil over medium heat. Add the diced onion and sauté for about 5 minutes until translucent. Stir in the minced garlic and cook for an additional minute until fragrant.

Add the sliced carrots, celery, and bell pepper to the pot. Cook for about 5-7 minutes, stirring occasionally, until the vegetables begin to soften.

Add the chicken pieces to the pot and cook until they are no longer pink, about 5 minutes.

Pour in the chicken broth and add the dried thyme, dried oregano, bay leaf, salt, and pepper. Bring the mixture to a boil, then reduce the heat and let it simmer for 20 minutes.

Stir in the fresh spinach, frozen peas, and corn. Simmer for an additional 5-10 minutes until the vegetables are tender.

Remove the bay leaf and stir in the lemon juice before serving. Adjust seasoning if necessary.