Wash chicken, pat dry, season with salt and pepper. Sprinkle half the oregano and garlic inside cavity. Melt butter in large frying pan. Brown chicken on all sides. Transfer to crockpot. Sprinkle with oregano and garlic. Add water to fry pan, stir to loosen brown bits. Pour into crockpot. Cover. Cook on Low 8 hours. Add lemon juice in the last hour of cooking.
Transfer chicken to cutting board. Skim fat. Pour juice into sauce bowl. Carve bird. Serve with some juice spooned over chicken.