In a large pot, heat the oil over medium heat. Add the onions, carrots and celery and cook, stirring occasionally, until the vegetables are crisp-tender, about 12 minutes. Add the garlic, thyme, oregano, red pepper, salt and black pepper; cook garlic for about 1 minute.
Add the potatoes and tomato paste and cook, stirring often, until the tomato paste begins to brown on the bottom of the pot for about 3 to 4 minutes.
Add in the vegetable stock and diced tomatoes with their juices and bring to a boil over medium-high heat. Lower the heat and simmer, partially covered, until the potatoes are tender, 20 to 28 minutes.
Stir in the green beans, corn and peas, return to a simmer and cook until the green beans are tender, for additional 4 to 5 minutes more.
Turn off the heat, add the spinach, parsley and vinegar, stirring until the spinach is slightly cooked. Taste and season with salt and pepper, if desired.
Serve hot, topped with more parsley.
