Muriel was considered by many to be the greatest softball pitcher in Saskatchewan. Her career started in 1936 when she pitched and won all her games as a member of the Tessier Millionaires.
From 1938 to 1945, she performed for the Saskatoon Pats. She did however, take one year off in 1943 to play for the South Bend White Sox of Chicago in the All-American Girls League. In 1946, Muriel joined the Saskatoon Grey Cab Ramblers. She helped the club win three successive Saskatchewan championships in 1946, 1947, and 1948, and two Western championships in 1946, and 1947. In 1950, Coben moved to Edmonton, joined the Mortons ball club and aided them in winning the Canadian championship over a very strong Toronto squad in 1952.
She returned to Saskatoon, again starred with the Ramblers until her playing days were over. Muriel was inducted into the Saskatchewan Sports Hall of Fame in 1979.