Airway clearance techniques (ACTs) are recommended for patients with stable non-cystic fibrosis (non-CF) bronchiectasis, but the efficacy of oscillating positive expiratory pressure (PEP) therapy compared to other techniques has not been reviewed. A systematic review of studies was conducted in stable patients comparing the effect of oscillating PEP therapy to other ACTs or a control condition. Data were extracted related to sputum expectoration, lung function, gas exchange, quality of life (QOL), symptoms, and exacerbation rate. Seven studies were included with a total of 146 patients, with a mean (SD) PEDro score of 7(1). Oscillating PEP therapy enhanced sputum expectoration compared to no treatment, but has equivalent benefits as the active cycle of breathing technique with gravity-assisted drainage (mean difference [95% CI] -2.8 g [-8.8 to 3.2 g]). Oscillating PEP has a similar effect as other ACTs on dynamic lung volumes, gas exchange and breathlessness. Use of oscillating PEP improved disease-specific QOL (p < 0.001) and cough-related QOL (p < 0.002) compared to no treatment but did not reduce exacerbation rate. In conclusion, in stable non-CF bronchiectasis, oscillating PEP therapy is associated with improvement in sputum expectoration and QOL compared to no treatment. Compared to other ACTs, the effect upon sputum expectoration, lung function, gas exchange, and symptoms are equivalent.