In a large bowl, mix together the first 6 ingredients and season to taste. Slash the chicken breasts 5-6 times, without cutting all the way through.
Add the chicken breasts and vegetables to the lactose free yogurt mix and stir to coat everything completely. Cover and leave the flavours to mingle for 10 mins.
Place a griddle over a high heat and cook the chicken and pepper for 4 mins each side until the chicken is cooked through and the grill lines are golden. Leave to rest for 2 mins before serving with steamed rice.