The investigation was made public last month and was instigated by a complaint from Norwegian browser company Opera.
Sundar Pichai, vice president for product management at Google, said in a blog: "We are applying to become a third party in the European Commission's proceedings."
The European Commission (EC) has confirmed it has sent a statement of objections to Microsoft about the tying of the Internet Explorer browser to the Windows operating system. The EC said: "It harms competition between web browsers, undermines product innovation and ultimately reduces consumer choice."
Earlier this month, Mozilla's Mitchell Baker, whose firm distributes the Firefox browser, said: "Microsoft's business practices have fundamentally diminished - in fact, came very close to eliminating - competition, choice and innovation in how people access the Internet."
Google recently launched its own Chrome web browser. Microsoft still controls around 75% of the browser market.
Read more about the EC and Microsoft: