Abstract Oscillatory baffled reactors (OBRs) are a form of plug flow reactor, ideal for performing long reactions in continuous mode, as the mixing is independent of net flow rate leading to more compact and practical designs. Mesoscale OBRs are currently being developed for laboratory-scale processes. The systems are designed to scale-up to industrial scale directly, or to be used as small-scale production platforms in their own right. Three different meso-reactor baffle designs (integral baffles, helical baffles and axial circular baffles (or “central”) baffles) were developed. These designs were chosen, as they are easily fabricated at “mesoscales” (here typically ∼5 mm diameter) and can be operated at low flow rates (μl/min to ml/min), whereas conventional designs of OBRs cannot. It was found that an increase in the net flow Reynolds number increased the optimum range of oscillatory Reynolds numbers over which plug flow can be achieved. The oscillation conditions had little effect on the residence time distribution behaviour at net flow Reynolds numbers above 25. These designs are effective and robust in scaled-down production of high added value products and decreasing the reagents required.