Dissolution of CO 2 in water was studied for a batch vertical multiorifice baffled column (MOBC) with varying orifice diameters (d 0 ) of 6.4−30 mm and baffle open area (α) of 15−42%. Bubble size distributions (BSDs) and the overall volumetric CO 2 mass transfer coefficient (K L a) were experimentally evaluated for very low superficial gas velocities, U G of 0.12− 0.81 mm s −1 , using 5% v/v CO 2 in the inlet gas stream at a range of fluid oscillations (f = 0−10 Hz and x 0 = 0−10 mm). Remarkably, baffles presenting large d o = 30 mm and α = 36%, therefore in the range typically found for single-orifice oscillatory baffled columns, were outperformed with respect to BSD control and CO 2 dissolution by the other baffle designs or the same aerated column operating without baffles or fluid oscillations. Flow visualization and bubble tracking experiments also presented in this study established that a small d o of 10.5 mm combined with a small value of α = 15% generates sufficient, strong eddy mixing capable of generating and trapping an extremely large fraction of microbubbles in the MOBC. This resulted in increased interfacial area yielding K L a values up to 65 ± 12 h −1 in the range of the U G tested, representing up to 3-fold increase in the rate of CO 2 dissolution when compared to the unbaffled, steady column. In addition, a modified oscillatory Reynolds number, Re o ′ and Strouhal number, St′ were presented to assist on the design and scale-up of gas−liquid systems based on multiorifice oscillatory baffled columns. This work is relevant to gas−liquid or multiphase chemical and biological systems relying on efficient dissolution of gaseous compounds into a liquid medium.