Preheat the grill to medium-high heat. If using wooden skewers, soak them in water for 30 minutes to prevent burning.
In a large bowl, combine the olive oil, balsamic vinegar, garlic powder, oregano, salt, and black pepper. Whisk until well blended.
Add the cherry tomatoes, bell pepper, zucchini, yellow squash, red onion, and mushrooms to the bowl. Toss until all the vegetables are evenly coated with the marinade.
Thread the marinated vegetables onto the skewers, alternating between different types for a colorful presentation.
Place the skewers on the grill and cook for 10-15 minutes, turning occasionally, until the vegetables are tender and slightly charred.
Remove from the grill and let cool for a few minutes before serving.