In windows 2000 and later there was a "FINDSTR" command that worked a bit like unixes "grep" command, and could search over multiple files.
According to wikipedia it was in a windows 2000 resource pack as "qgrep" but appeared in other editions as a native command "FINDSTR". I remember using it but not in what versions of DOS it appeared.
https://en.wikipedia.org/wiki/Findstr