Recent work using a large-charge effective field theory (EFT) for the O(N) Wilson-Fisher conformal field theory has shown that the anomalous dimensions of large-charge operators can be expressed in terms of a few low-energy constants (LECs) of the EFT. By performing lattice Monte Carlo computations at the O(N) Wilson-Fisher critical point, we compute the anomalous dimensions of large-charge operators up to charge Q=10, and extract the leading and subleading LECs of the O(N) large-charge EFT for N=2,4,6,8. To alleviate the signal-to-noise ratio problem present in the large-charge sector of conventional lattice formulations of the O(N) theory, we employ a recently developed qubit formulation of the O(N) nonlinear sigma models with a worm algorithm. This enables us to test the validity of the large-charge expansion, and the recent predictions of large-N expansion for the coefficients of the large-charge EFT.