Lattice matched GaAs/AlGaAs epitaxial structures with quantum dots are studied under static uniaxial stress applied either along the [001] or [110] crystal directions. We conduct simultaneous measurements of the spectral shifts in the photoluminescence of the bulk GaAs substrate, which relate to strain via deformation potentials a and b, and the quadrupolar shifts in the optically detected nuclear magnetic resonance spectra of the quantum dots, which relate to the same strain via the gradient-elastic tensor S ijkl . Measurements in two uniaxial stress configurations are used to derive the ratio b/a = 0.241 ± 0.008 in good agreement with previous studies on GaAs. Based on the previously estimated value of a ≈ −8.8 eV we derive the product of the nuclear quadrupolar moment Q and the S-tensor diagonal component in GaAs to be QS11 ≈ +0.76×10 −6 V for 75 As and QS11 ≈ −0.37 × 10 −6 V for 69 Ga nuclei. In our experiments the signs of S11 are directly measurable, which was not possible in the earlier nuclear acoustic resonance studies. Our QS11 values are a factor of ∼1.4 smaller than those derived from the nuclear acoustic resonance experiments [Phys. Rev. B 10, 4244 (1974)]. The gradient-elastic tensor values measured in this work can be applied in structural analysis of strained III-V semiconductor nanostructures via accurate modelling of their magnetic resonance spectra. arXiv:1804.06879v2 [cond-mat.mes-hall] 1 May 2018