The Obama administration has now released the documents that it said it would regarding the NSA's phone record collection program. You can read them here. For the most part, they don't tell us anything we didn't already know, but a DOJ letter in 2009 does shed some light on how much Congress knew about this program. A relevant excerpt is below. This letter was made available to all members of Congress (under the usual strict secrecy rules), and it makes clear that (a) NSA collects "substantially all" of the domestic phone records of U.S. phone companies, (b) ditto for emails, and (c) they use these records to perform contact chaining.
Whatever else you think about these programs, these letters suggest to me that members of Congress knew all of the basics of what NSA was doing. Complaints that they were kept in the dark, or that the programs were more extensive than they were led to believe, don't have much to support them.