Preheat oven to 200℃ and drizzle oil over the bottom of a large roasting tray.
Place chicken in roasting tray and pat dry using paper towel. Smother chicken all over with softened butter and sprinkle over garlic salt and pepper. Squeeze lemon over chicken and stuff used lemon wedge inside chicken along with garlic cloves.
Bake chicken for 1.2-1.5 hours or until juices run clear when pierced in the thigh. The internal temperature should read 65℃ on a meat thermometer. Allow the chicken to rest for 10-15 mins before carving and serve.