Heat olive oil in a large pot over medium heat.
Add the diced onion and sauté for about 5 minutes.
Stir in the minced garlic and cook for another minute.
Add the chopped bell pepper and cook for another 5 minutes.
Incorporate the diced zucchini and eggplant, stirring to combine.
Add the diced tomatoes and vegetable broth, then stir in the thyme.
Season with salt and pepper, adjusting to taste.
Bring the soup to a gentle boil, then reduce heat to simmer for 25-30 minutes.
Remove from heat and let cool slightly before blending, if desired.
Serve warm, garnished with fresh basil.