Margareta von Ascheberg was the youngest child of Field Marshal Rutger von Ascheberg and Magdalena Eleonora Busseck. On 26 January 1691, she married colonel count Kjell Christopher Barnekow (d. 1700) in Malmö. As was the custom of the Swedish nobility as that time, she kept her name after marriage and style herself »Grevinnan Ascheberg» (Countess Ascheberg). The couple had four children. She accompanied her spouse on his military commissions: she gave birth to their youngest sons during the Bombardment of Brussels in 1695.