OER or Oer may refer to:
Science Oxygen enhancement ratio, effect magnitude of ionizing radiation due to the presence of oxygen Oxygen Evolution Reaction, the formation of oxygen by electrochemical reduction of water
Transport Odakyu Electric Railway, a Japanese railway company Oregon Electric Railway, an interurban railroad line in Oregon, United States Örnsköldsvik Airport in Örnsköldsvik, Sweden
Other uses Oer family, a German noble family Oer-Erkenschwick, a town in North Rhine-Westphalia, Germany Offense efficiency rating, the average number of points scored per shot by a basketball player Officer Evaluation Report, an evaluation form used by the United States Army Open educational resources, open documents that are useful for teaching, learning, educational, assessment and research purposes Owner’s Equivalent Rent, an economic metric for housing prices often used in the calculation of market baskets