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What was your egg setup? An hour and fifteen minutes is about thirty minutes more than what it takes me to cook them? How big were the chickens? Have you checked your thermostat? I cook my spatchcocks at 350 degrees, indirect in less than 45 minutes. Now my chickens are fresh locally raised chickens and 3 to 4 pounds, and cooked high in the dome. I brine them 12 to 24 hours ahead of cooking. I use different poultry seasonings, but the chicken always comes out great, and never tough. Sometimes my thigh finish temperature my end up around 190 internal degrees as the breast hit 165 degrees, but the meat is still tender and full of juices. Also was your egg "completely" stabilized before loading the chicken onto the grill?