Wash and chop the vegetables. Slice the cucumber into rounds then slice each one into quarters. Slice the red onion into thin strips. Slice the grape tomatoes in half.
Mix together the salad dressing ingredients in a small bowl: olive oil, red wine vinegar, granulated sugar, dried basil, salt and basil.
Add the chopped vegetables to a large bowl. Drizzle the salad dressing overtop. Toss everything together. Cover with a lid or plastic wrap and place in the fridge for 2 hours to let vegetables absorb the dressing flavors. Stir together just before serving.