Quantum dots of InSb and GaSb were grown on GaAs(001) by molecular-beam epitaxy. In situ scanning tunneling microscopy measurements taken after 1-2 monolayers of InSb or GaSb growth reveal the surface is a network of anisotropic ribbon-like platelets. These platelets are a precursor to quantum dot growth. Transmission electron microscopy measurements indicate that the quantum dots are coherently strained. Quantum dots of InSb and GaSb capped by GaAs exhibit strong luminescence near 1.1 eV.