Both the birthplace of Margaret Oh and how she became a Catholic are unknown. She married Francis Pak and lived in Cheongju, Chungcheong-do. When the Byeongin Persecution broke out in 1866, the couple took their four sons and moved to Jeolgol, Jincheon (now, Baekgok-myeon, Jincheon-gun). They practiced their religion in secret.
  
   Margaret Oh‘s family lived in peace in Jeolgol for two years. They faithfully practiced their religion. they were faced with danger when the persecution got tougher in 1868. On September 5 of that year (July 19, by the Lunar calendar), the police of Juksan, Gyeonggi-do invaded Jeolgol.
  
   When Francis Pak`s family heard that the police were coming, they escaped into the mountain. When they were escaping they scattered in all directions. While hiding in the mountain Margaret Oh was arrested with her baby on her back. She was beaten mercilessly.
  
   Her husband Francis, who was anxious about the whereabouts of his family, came down from the mountain. He was arrested by the police. Margaret Oh and Francis Pak were taken to the prison in Juksan. Her husband, Francis Pak, wrote from the prison to his younger brother Philip and his eldest son Anthony. He made the following recommendation to his brother:
  
   "Please, take care of your little nephews, and worship the Lord with a sincere heart. Obey the Divine ordinance, and follow me."
  
   His letters were lost in a fire with other religious objects during the persecution. Margaret Oh and her husband Francis Pak defended their faith while enduring all kinds of punishment. Together they were martyred in Juksan on September 28, 1868 (August 13, by the Lunar calendar).