In a large bowl, combine the yogurt, olive oil, garlic, cumin, coriander, chili powder, garam masala, salt, and pepper.
Add the chicken cubes and mix to coat evenly.
Cover and refrigerate for at least 30 minutes, or up to 24 hours.
Preheat the grill to medium-high heat.
Grill the chicken for 4-5 minutes per side, or until cooked through.
Serve with grilled vegetables and warm naan bread.