Heat olive oil in a large pot over medium heat.
Add the diced onion and garlic, cooking until translucent.
Stir in the diced eggplant and bell pepper; cook for 5–7 minutes.
Add the zucchini and tomatoes, stirring to combine.
Pour in the vegetable broth and add the thyme and bay leaf.
Season with salt and pepper, then bring to a simmer.
Let it simmer for about 25–30 minutes until vegetables are tender.
Remove the bay leaf and adjust seasoning if necessary.
Ladle soup into bowls and garnish with fresh basil.