In a club career sometimes disrupted by injury, Margrét Lára represented ÍBV and Valur of the Icelandic Úrvalsdeild, Duisburg and Turbine Potsdam of the Frauen-Bundesliga, and Linköpings and Kristianstads DFF of the Damallsvenskan.

[4] In the 2008 WPS International Draft, Margrét Lára was selected by the Los Angeles Sol but decided not to join the Women's Professional Soccer team.

"[5] At Linköpings Margrét Lára struggled to replicate her earlier form and started four of her 12 matches in the first half of the season, scoring twice.

Although Kristianstads were a lower ranked team, she was happy to move in order to reunite with Elísabet Gunnarsdóttir – who had been her coach at Valur.

[6] She won the Damallsvenskan top scorer award in 2011, tied at 16 goals with Manon Melis of LdB FC Malmö.

She immediately scheduled surgery to fix the issue which had inhibited her training for several seasons and caused her to operate at 70% of her true level.

[10] Before the 2013 Damallsvenskan season, Kristianstads gave a trial to Margrét Lára's visiting sister Elísa in a pre-season friendly, but had no immediate plans to sign the younger Viðarsdóttir to a contract.

[17] Margrét Lára made her first appearance for the Iceland senior national team on 14 June 2003, in a 2005 UEFA Women's Championship qualification match against Hungary at Laugardalsvöllur.

[18] Four years later, national team coach Siggi Eyjólfsson selected Margrét Lára in the Iceland squad for UEFA Women's Euro 2013.

With Margrét Lára on maternity leave, incoming national coach Freyr Alexandersson appointed Sara Björk Gunnarsdóttir as the new team captain in 2014.