Energy levels, radiative transition probabilities, and autoionization rates for B-like oxygen (O 3+) including 1s 22s 2 nl, 1s 22s2p nl, and 1s 22p 2 nl ( n = 2–8, l ⩽ n − 1) states are calculated using the multiconfiguration interaction Cowan code and a relativistic many-body perturbation theory method (RMBPT) code. Autoionizing levels above three thresholds (1s 22s 2 1S, 1s 22s2p 3P, and 1s 22s2p 1P) are considered. Configuration mixing (2s 2 nl + 2p 2 nl) plays an important part in all of the atomic properties considered. Branching ratios relative to the first threshold and the intensity factor are calculated for satellite lines and dielectronic recombination rate coefficients for the excited 105 odd-parity and 94 even-parity states. The dielectronic recombination rate coefficients are calculated including 1s 22s 2 nl, 1s 22s2p nl, and 1s 22p 2 nl ( n = 2–8, l ⩽ n − 1) states. The contribution from the excited states higher than n = 8 are estimated by extrapolation of all atomic properties to derive the total dielectronic recombination rate coefficient. The orbital angular momentum quantum number distribution of the rate coefficients shows a peak at l = 5. The total dielectronic recombination rate coefficient is derived as a function of electron temperature and the dielectronic satellite lines are also obtained. The state selective dielectronic recombination rate coefficients to excited states of B-like oxygen are obtained, which are useful for modeling O IV spectral lines in a recombining plasma.