In this paper, we study one-stage explicit extended Runge--Kutta--Nystr\"{o}m
(ERKN) integrators for solving quasilinear wave equations. We introduce ERKN
integrators as the semidiscretization in time. It is shown that one-stage
explicit ERKN integrators in time have second-order convergence. By using a
Fourier spectral method in space, full-discrete ERKN integrators are presented.
Error bounds of this fully discrete scheme are also derived without requiring
any CFL-type coupling of the discretization parameters. The error analysis
given in this paper is based on energy techniques, which are widely applied in
the numerical analysis of methods for partial differential equations.