In a draft plan for a "digital single market" encompassing everything from online shopping to telecoms regulation, the commission said it would probe how online platforms list search results and how they use customer data. The latest draft of the plan, seen by the FT, will be approved by the commission next week.
The plan could also bring in stricter rules for video-on-demand services such as Netflix and messaging apps like WhatsApp and Skype that have become big rivals to traditional European media and telecoms companies.
Companies such as Airbnb and Uber are also likely to be roped into any investigation into platforms, which will aim to determine whether they are abusing their market power in the so-called "sharing economy".
The EU's intensifying assault on big American tech groups has triggered accusations in the US, including from President Barack Obama, that the bloc is engaging in protectionism.
The plan for a "comprehensive assessment" of online platforms comes after French and German ministers urged the EU to launch an investigation into the role played by the US internet giants.
Read MoreHow Google might have to change to please the EU
Earlier this week, the French economic minister Emmanuel Macron and German economic minister Sigmar Gabriel called for a "general regulatory framework for 'essential digital platforms'" in a letter to the commissioner overseeing the reforms that was seen by the FT.
They wrote: "We believe that the growing power of some digital platforms is a wider challenge that warrants a policy consultation with the aim of establishing an appropriate general regulatory framework for'essential digital platforms'."
The commission will start the probe "before the end of 2015", according to the draft. It will look at the role of paid-for links and advertisements in search results, along with the ability of individuals and businesses to move from platform to platform.
"Some online platforms have evolved to become players competing in many sectors of the economy and the way they use their market power raises a number of issues that warrant further analysis beyond the application of competition law in specific cases," the 17-page document reads,in a clear reference to the Google antitrust case.
Elsewhere in the draft, the commission said that it will "review" whether on-demand services such as Netflix should be subject to the same rules as traditional TV broadcasters. According to the document, on-demand services are sometimes "subject to lower obligations" than their television peers.
Other measures to be proposed include plans to make it easier for small merchants in the EU to sell goods to customers in other countries. As part of the measures, ecommerce groups would be subject to their own national laws rather than the buyer's as well as a set of EU-wide contractual rights. The commission will also crackdown on the opaque pricing structures used by parcel companies for deliveries between EU countries.
More from the FT:
Silicon Valley braced for EU scrutiny
Google turns on the charm in Europe
EU threatens internet
The commission said it would launch long-awaited copyright reform before the end of this year, which will probably spark a tussle between large media groups, artists and producers as well as consumer groups.
Brussels will aim to introduce the "full portability of legally acquired content" and allow "cross border access to legally purchased online services". A crackdown on online piracy will focus on "commercial scale infringements", rather than individual abuses.
Finally, the commission will launch another attempt to reform telecoms regulation in the EU, to apply the same rules for traditional telecoms groups and internet rivals such as WhatsApp and Skype.