A pre-assembled internal frame for a modular wall comprises a pair of vertical frame members. Each first flange of the vertical frame member has a pair of series of vertically arranged mounting openings, and each second flange has a single series. The vertical frame members are oriented to enable the frame to be arranged in an end to end junction with another frame with adjacent vertical frame members thereof abutting. This provides three of the series of vertically arranged openings on each side of the modular wall at the end to end junction. A fastener is positioned in a fastener receiving portion for fastening the horizontal frame member to the vertical frame members. The fastener receiving portions are recessed laterally inwardly from the first and second web sections for avoiding interference between adjacent fasteners when the frame is arranged in the end to end junction with another such frame.