The groups said Verizon had not made some of its documents available in electronic form and would have charged them thousands of dollars for paper copies.
In a filing with the FCC on Monday, Verizon and the cable companies revealed they had met with top FCC officials on Friday.
In that meeting, the companies all offered to provide the documents in PDF form and to create an electronic index to sort through the materials.
The companies insisted that they had already "complied with the technical and formatting specifications contained in the commission's instructions," but that they were willing "to take certain additional steps to facilitate third-party review of the materials."
The deal would allow Verizon to buy a block of wireless spectrum from Comcast, Cox, Time Warner and Bright House. The companies have also agreed to cross-sell each other's services.
Opponents of the deal worry that the additional spectrum could allow Verizon to dominate the wireless market and that the side deals will limit competition.
Verizon says the additional spectrum will help it meet the growing demands of mobile devices and the side deals will give consumers more options.