Preheat the grill to medium-high heat (approximately 375°F to 400°F / 190°C to 204°C).
Wash and cut the zucchini and yellow squash into 1/2-inch thick rounds. Cut the bell peppers into quarters, remove the seeds, and chop the red onion into wedges.
In a mixing bowl, combine the sliced vegetables (zucchini, yellow squash, red and yellow bell peppers, red onion, and cherry tomatoes).
In a separate small bowl, whisk the olive oil, balsamic vinegar, garlic powder, dried oregano, salt, and pepper to create a marinade.
Pour the marinade over the mixed vegetables and toss until they are evenly coated.
Use tongs to place the vegetables directly on the grill. Grill for about 10-15 minutes, turning occasionally, until the vegetables are tender and have grill marks.
Once done, remove from the grill and let cool for a couple of minutes.
Transfer the grilled veggies to a serving platter and garnish with fresh basil if desired.
Feel free to customize this recipe with your favorite vegetables, such as asparagus, eggplant, or mushrooms.