Rovibrational spectroscopy of the fundamental OH stretching mode of the trans-HOCO radical has been studied via sub-Doppler high-resolution infrared laser absorption in a discharge slit-jet expansion. The trans-HOCO radical is formed by discharge dissociation of H2O to form OH, which then combines with CO and cools in the Ne expansion to a rotational temperature of 13.0(6) K. Rigorous assignment of both a-type and b-type spectral transitions is made possible by two-line combination differences from microwave studies, with full rovibrational analysis of the spectrum based on a Watson asymmetric top Hamiltonian. Additionally, fine structure splittings of each line due to electron spin are completely resolved, thus permitting all three e, Sbb, Ea spin rotation constants to be experimentally determined in the vibrationally excited state. Furthermore, as both a- and b-type transitions for trans-HOCO are observed for the first time, the ratio of transition dipole moment projections along the a and b principal axes is determined to be mu(a)/mu(b) = 1.78(5), which is in close agreement with density functional quantum theoretical predictions (B3LYP/6-311+ +g(3df,3pd), mu(a)/mu(b) = 1.85). Finally, we note the energetic possibility in the excited OH stretch state for predissociation dynamics (i.e., trans-HOCO -> H + CO2), with the present sub-Doppler line widths providing a rigorous upper limit of >2.7 ns for the predissociation lifetime.