Al-Sc alloys are strengthened by nanoscale Al<sub>3</sub>Sc precipitates. By alloying with faster-diffusing Er and slower-diffusing Zr additions, complex core/double-shell precipitates are formed, with precipitates consisting of an Er-enriched core surrounded by a Sc- and Zr-enriched shells. The Er-enriched core enhances strength while the Zr-enriched outer shell improve thermal stability. The present study seeks ultimate strength and coarsening resistance by alloying Al-Er-Sc-Zr alloys with Group 5 additions (M = V, Nb, Ta), which are expected to be slower diffusers than Zr. By sequential nucleation of the constituent solutes we have engineered Al<sub>3</sub>(Er,Sc,Zr,M) precipitates with core/triple shell compositions. Relationships between the observed mechanical properties and the precipitate sizes and compositions are established using atom-probe tomography throughout the microstructural evolution of the alloys.