A theoretical model for isotopologues of beryllium monohydride, BeH, BeD and BeT, A 2 Π to X 2 Σ + visible and X 2 Σ + to X 2 Σ + infrared rovibronic spectra. The MARVEL procedure is used to compute empirical rovibronic energy levels for BeH, BeD and BeT, using experimental transition data for the X 2 Σ + , A 2 Π, and C 2 Σ + states. The energy levels from these calculations are then used in the program Duo to produce a potential energy curve for the ground state, X 2 Σ, and to fit an improved PEC for the first excited state, A 2 Π, including a spin-orbit (LS) coupling term, a Λ– doubling state to state (A-X states) coupling term, and Born-Oppenheimer breakdown (BOB) terms for both curves. These, along with a previously computed ab initio dipole curve for the X and A states are used to generate vibrational-rotational wavefunctions, transition energies and A-values. From the transition energies and Einstein coefficients accurate assigned synthetic spectra for BeH and its isotopologues are obtained at given rotational and vibrational temperatures. The BeH spectrum is compared with a high resolution hollow-cathode lamp spectrum and the BeD spectrum with high resolution spectra from JET giving effective vibrational and rotational temperatures. Full A – X and X — X linelists are given for BeH, BeD and BeT and also provided on the ExoMol website.