An interesting cubic-shaped precipitate was observed in the matrix of a squeeze-cast Al-4.3 wt % Cu-2.0 wt % Mg/SiC composite which was heat-treated to a T7 condition. Although this phase had been observed by a few investigators in the past, it had never been examined in detail until now. This cubic phase generally had an edge length ranging from 30 to 50 nm and existed in volume fractions as high as 3.8 %. Theoretical strengthening models predicted this phase to have good potential for precipitate strengthening. In addition, the cubic phase exhibited a low rate of coarsening at temperatures as high as 250-degrees-C; apparently due to its low interfacial energy. Consequently, this cubic precipitate shows potential for increasing the useful temperature range of aluminium alloys and composites and could be of great importance to the aerospace and automotive industries.