Heat a drizzle of oil in a large pot over medium heat. Add the diced onion and cook for 4 to 5 minutes, stirring occasionally, until soft and lightly golden. Add the garlic and cook for 30 seconds until fragrant.
Add the chopped vegetables, starting with any harder vegetables like carrots or potatoes. Cook for 3 to 4 minutes, stirring, to begin softening them and build flavour. Add softer vegetables like zucchini or cabbage after a couple of minutes if using (if using baby spinach or similar, hold off adding until the soup has completely cooked, then stir through until just wilted).
Add the dried oregano or mixed herbs, bay leaves, tomatoes and stock. Stir well, scraping the bottom of the pot to lift any flavour, and bring to a gentle boil.
Reduce the heat to a simmer and cook for 20 to 25 minutes, stirring occasionally, until all the vegetables are tender. Taste a piece to check doneness.
Taste and adjust with salt if needed. If the soup is too thick, add a little water or stock to loosen it. Serve hot. Garnish with cracked black pepper and serve with fresh crusty bread or toast if desired.