Supersymmetry predicts that gauge couplings are equal to the corresponding gaugino-sfermion-fermion Yukawa couplings. This prediction can be tested for the QCD sector of the MSSM by studying the processes e"+e"- #-># squark+antisquark+gluon and e"+e"- #-># squark+antiquark+gluino at a future linear collider. We present results for these processes at next-to-leading order in #alpha#_s in the framework of the MSSM. We find sizable SUSY-QCD corrections. The renormalization scale dependence is significantly reduced at next-to-leading order. (orig.)SIGLEAvailable from TIB Hannover: RA 2999(02-097) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman