Set up your Q for direct cooking. Place the casserole dish (without lid) in the centre of the Q and add the oil. Preheat on high for ten minutes.
Oil the drumsticks and season with salt and pepper.
Once the Q is preheated, leave the heat setting on high. Add the onion and garlic to the casserole dish and cook, stirring occasionally, for 2-3 minutes. At the same time, add the chicken to the grill and cook for 2-3 minutes per side. Once you have turned the chicken, remove the casserole dish from the Q using the detachable handles.
Add the undrained tomatoes and stock to the casserole and stir through.
Turn the Q to the roast setting and add a convection tray and trivet using tongs and/or heat proof gloves. Place the lid on the casserole dish (turning the vent control to steam) and place on the trivet. Cook for 1 hour.
Remove the casserole lid and cook for a further 25-30 minutes, or until the chicken is tender and the sauce has reduced and thickened slightly.
Add the olives, parsley and oregano and cook for a further 5-10 minutes or until heated through.