In a large bowl, combine the yogurt, vegetable oil, lemon juice, minced garlic, ground cumin, paprika, black pepper, salt, and oregano or thyme if using. Mix well.
Add the meat cubes to the marinade, ensuring they are well coated. Cover and refrigerate for at least 2 hours, or preferably overnight for best flavor.
While the meat is marinating, prepare the vegetables by cutting them into chunks.
Thread the marinated meat, onion, bell pepper, zucchini, and cherry tomatoes onto skewers, alternating between meat and vegetables.
Preheat your grill to medium-high heat.
Place the skewers on the grill and cook, turning occasionally, until the meat is cooked through and has a nice char, about 15-20 minutes depending on the size of the meat cubes and the heat of the grill.
Enjoy your meal!