In a bowl, whisk together olive oil, balsamic vinegar, minced garlic, oregano, salt, and black pepper.

Place chicken breasts and steak in a resealable plastic bag. Pour marinade over the meats, seal the bag, and refrigerate for at least 30 minutes.

Toss sliced bell peppers, zucchini, and red onion with a little olive oil, salt, and pepper.

Preheat the grill to medium-high heat.

Remove meats from marinade and grill chicken for about 6-7 minutes per side, and steak for about 4-5 minutes per side, or until cooked to desired doneness.

Grill the vegetables in a grill basket for about 10-12 minutes, stirring occasionally, until tender and slightly charred.

Remove meats and vegetables from the grill. Let the meats rest for a few minutes before slicing. Serve hot.