One of the missing features of Gedit is the "search in files" functionality.
I'm going to describe how this can be easily added without installing any additional plugin.
This method uses the "External tools" plugin (which comes in bundle with gedit) and "Gnome Search Tool" (gnome's default search tool).
1) open Gedit and enable the "External tools" plugin in Edit >> Preferences >> Plugin
2) don't close the dialog but select the plugin and click "Configure plugin" instead
3) let's add a new tool with the following properties
Name : Find in files (or whatever you want)
Description : Find in files (or whatever you want)
Accelerator (the keybord shortcut) : type <Control><Shift>f (or whatever you want - be sure it's not already used)
Input : current selection
xargs gnome-search-tool --contains
Output: bottom panel
Scope: all documents
4) Close the dialog
You can test the newly added tool via the shortcut you've inserted or Tools >> Find in files
You can also select some text while editing a file and search for that in files
If you have an easier way to achieve this or even add "Search and replace in files" functionality feel free to contribute and i'll update the post.