After much reading, I figured out the problem. Turns out it had nothing to do with UEFI.
My Windows 7 drive had some RAID 0 metadata on it. My PC does NOT have a RAID array, but my OEM set it up this way for some reason. Apparently this metadata interferes with GRUB2's ability to search the drive. Therefore you have to remove the metadata.
If your PC does have a RAID array, this may not work and you may lose your data. Either backup your data or ask someone who knows more about RAIDs.
First, I backed up the metadata, so I could replace it if Windows didn't boot afterwards:
dmraid -D -r
dmraid(8) explains this more.
Then I did the following commands:
dmraid -E -r
GRUB was able to see Windows after this.