We use convariant harmonic-oscillator wave functions to describe quark-model hadrons in Glauber's model of diffractive scattering. It is shown that the Glauber model can be constructed in the center-of-mass system in terms of fully covariant quantities. For elastic scattering, the covariant model gives the same result as that using nonrelativistic harmonic-oscillator wave functions. For the transition from the $n=0$ to $n=2$ states, which includes the diffractive excitations to the $N(1470)$ and $N(1690)$ resonances, the relativistic effect is simply a multiplication of the nonrelativistic amplitude by the factor ($1\ensuremath{-}{\ensuremath{\alpha}}^{2}$), $\ensuremath{\alpha}$ being the velocity difference between the incoming nucleon and the final-state resonance. We discuss the effects of these results on the existing nonrelativistic calculations.