Abstract: A pre-finished insulated panel building system preferably includes a base member, a cover member and a decorative coating. A moisture barrier sheet is preferably attached to an exterior surface of a building. A drainage and ventilation mat is attached to the moisture barrier or directly to the exterior surface of the building. The base member is preferably a rectangular block, which is attached to an interior or exterior surface of the building. The cover member includes a base cavity formed in a bottom thereof. A perimeter of the base cavity is sized to receive an outer perimeter and height of the base member. Alternatively, the cover member is secured to the base member with a pair of snap rails. Each snap rail includes a base rail member and a cover rail member. The top and outer perimeter of the cover member is sprayed with the decorative coating.