Slice onion, tomato, zucchini, cucumber, green pepper, avocado evenly.
In a ziplock bag, add extra virgin olive oil, oregano, salt, and all the vegetables except avocado. Rest it for 5 minutes.
Grill all the vegetables.
Grill the bread on both the sides.
Start stacking the grilled veggies over a slice of bread in the order of onion, bell pepper, zucchini, tomato, cucumber, avocado and end with the bread.
Serve hot with Tomato Ketchup or mustard sauce.
Notes
Do not need to marinate the cucumber and avocado. Slice it before serving.