Select all, goto Object > Compound Path > Make, recolor the shape; It's now like one.
The upper AbC is an outlined text. The lower is after making a compound path and recoloring.
CAUTION: Compound path is the way to make holes. If you release the compound path, you will create a mess. The holes you already had, get filled:
You can remake the holes by ungrouping at first and then selecting the parts of one letter at a time and making a compound path.