These two commands first save the grep results to a temporary file and then populate Vim's quickfix list with the contents.
$ grep FooBar -irn ./src/app > /tmp/quickfix
$ vim -q /tmp/quickfix
-i makes the search case insensitive, the
-r performs a recursive search on all descendent directories, and the
-n includes line numbers in the grep output. Those line numbers are important for Vim's quickfix list.
Once in Vim, use
:cn to navigate to the next item in the quickfix list.
See also: https://askubuntu.com/a/1100036/500631