Oonk represented her nation at international competitions. Oonk competed at the 1995 and 1996 World Junior Speed Skating Championships. As an elite speed speed skater she participated at five World Single Distance Speed Skating Championships (1998, 1999, 2001, 2004 and 2005) and four times at the World Sprint Speed Skating Championships for Women (2000 (22nd), 2001 (31st), 2004 (14th) and 2005 (14th)). She also competed at other international competitions, including at ISU Speed Skating World Cups.