The deal is Google's biggest PPA wind commitment to date, bringing its total to 570MW.
The Happy Hereford farm is expected to be operational in late 2014 and is being developed by Chermac Energy, a Native American owned company in Oklahoma.
The farm will provide energy to the Southwest Power Pool, the regional grid that serves the internet company’s Oklahoma data centre.
Matt Pfile, Google’s data center energy and location strategy senior manager, said: "This type of power purchase agreement represents one of several ways we’re working to make additional renewable energy available for both our data centers and the communities in which we operate."
Pfile said: "Due to the current structure of the market, we can’t consume the renewable energy produced by the wind farm directly, but the impact on our overall carbon footprint and the amount of renewable energy on the grid is the same as if we could consume it."
In January, Google provided a $200 million equity investment in the 168MW Spinning Spur project, which is 56 kilometres from Amarillo.
The search company has signed a number of PPAs this year including the 72MW Maevaara wind farm in northern Sweden, Google's first in Europe, in June.
In January it signed an agreement with the Grand River Dam Authority to supply electricity from Atlantic Power Corporation-owned 48MW Canadian Hills wind farm in Oklahoma.
Google has set of goal of reducing its carbon footprint to zero and has invested more than $1 billion in renewable energy.