An electrical box assembly for mounting a security camera or electrical fixture on a wall or ceiling. The electrical box assembly includes an electrical box and a trim piece. A plurality of rotatable flags, adjustable from the front of the electrical box assembly, are tightened to secure the assembly to the wallboard in a ceiling or wall. Wall preparation for installation of the electrical box assembly requires only a round hole in the wallboard, which can be easily provided by a hole-saw. The flags can be rotated inward to enable easy insertion of the electrical box within the hole in the wallboard. The electrical box assembly includes a mounting bar and adapter plate that adapt the assembly for mounting a wide variety of security cameras and electrical fixtures. The electrical box assembly conforms to the electrical code in those areas that require a metallic box.