Preheat oven to 375 degrees. Before trussing the chicken season generously with salt and pepper on the outside and inside of the bird. Make your marinade- Mix half a cup of greek yoghurt, coriander, cumin, paprika, garlic powder, garam masala, chili powder and juice of 1/2 lemon. whisk until smooth and the spices have blended evenly with the yoghurt. Coat the cavity and outside of the bird evenly. Truss your chicken and place in a roasting pan.
Cut garlic head in half and place on opposite sides of the board. Drizzle with olive oil and cook covered for 1 hour and uncovered for the last 1/2 hour. Serve w/ crispy potatoes or turmeric rice and mixed green salad.