She made her debut for Kolbotn in 2010. On 6 August 2011, she scored three goals in seven minutes as Røa were beaten 4–1, with Andrine scoring the last goal. Aged 16, this made her the youngest player ever to have scored a hat-trick in Toppserien. While still 16 years old, she finished as Kolbotn's top scorer in the 2011 Toppserien season and was voted as the league's Young Player of the Year. Ahead of the 2012 season, both Hegerberg sisters joined Stabæk. During a match against Fart in May 2012, she scored five goals during the first half of Stabæk's 8–2 win. At this stage the sisters were considered to be two of the biggest talents in Norwegian women's football, and Ada won the Statoil "Talent of the Month" award for the second time in May 2012. She became top goalscorer in the 2012 Toppserien with 25 goals in 18 matches. She also contributed two goals in the semi-final of the 2012 Norwegian Women's Cup, when Amazon Grimstad were beaten 3–0. Stabæk's 4–0 final victory over Røa saw Hegerberg score a hat-trick.