M2M, a division of Manning Gottlieb OMD, pitched against three undisclosed agencies for the business, believed to be worth a seven-figure sum.
Robbie Morton, deputy managing director of M2M, said the agency had participated in BeatThatQuote's last review and knew the client's business well.
The agency recruitment process was handled by marketing director Nick Tsimbidaros.
, which was founded three years ago, finds the best rates across a wide range of financial products including loans, mortgages, credit cards, insurance and annuities.Last week, BeatThatQuote was named the UK's fastest growing website in 2007 by Nielsen Online, ahead of social networking site Facebook.
M2M also holds the offline buying accounts for dating website Match.com and online DVD rental service Lovefilm.