OS X comes with a powerful search tool called mdfind:
mdfind "text to find"
To search on a specific folder use the flag -onlyin /path/to/folder
Search using grep
Way more slower but also effective would be using grep command:
grep -sr "text to find" /path/to/folder
The flag -s is for ignoring errors, this way we will only get positive results on screen.
The flag -r is for a recursive search following all subfolders.