Find all files in the current directory (and its subdirectories) and execute a sed command on each of them to replace any string of the form "ABC DEF GHI" with "GHI DEF ABC".
find ./* -type f -exec sed -i 's/\([A-Z]\+\) \+\([^ ]\+\) \+\([A-Z]\+\)/\3 \2 \1/g' {} \;