Make the flavorful marinade: In a small bowl, whisk together the dried oregano, olive oil, rice vinegar, salt, and black pepper until everything is well combined. The dressing should smell fresh, herby, and slightly tangy.
Prepare the fresh salad ingredients: Add the finely chopped red onion, quartered cherry tomatoes, fresh mozzarella balls, and diced cucumber to a large mixing bowl. The colorful combination starts to look bright and summery.
Toss everything together: Pour the marinade over the salad ingredients and gently toss until everything is evenly coated. If you’re using fresh basil leaves, fold them in at the end for the freshest flavor.
Serve and enjoy: Transfer the vegan caprese salad to a serving bowl or platter and serve immediately. Enjoy it fresh as a light lunch, refreshing side dish, or easy summer appetizer.