In a large bowl, combine olive oil, balsamic vinegar, garlic powder, oregano, basil, salt, and black pepper. Whisk until well blended.
Add the sliced bell peppers, zucchini, red onion, and cherry tomatoes to the bowl. Toss the vegetables in the marinade until evenly coated.
Cover the bowl with plastic wrap and refrigerate for at least 30 minutes, or up to 2 hours for more flavor.
Preheat your grill to medium-high heat. If using skewers, soak wooden skewers in water for 30 minutes to prevent burning.
Thread the marinated vegetables onto skewers or place them directly on the grill in a grill basket.
Grill the vegetables for about 10-15 minutes, turning occasionally, until they are tender and have nice grill marks.
Remove from the grill and serve warm.