Cut zucchini, red onion wedges, bell pepper (seeded), and yellow squash into pieces about an inch.
Cook yellow corn cut into 3 parts for 5 minutes, drain and let cool.
Prepare the marinade by mixing Olive Oil Oregano, vinegar, garlic, mustard, thyme, salt, and pepper in small bowl.
In a zipper plastic bag, mix all ingredients and refrigerate at least 4 hours.
Remove vegetables from marinade. Thread vegetables onto skewers as desired and grill for 10 to 12 minutes, turning frequently.