Using & is fine for short commands, but that single line can get very long very quick. When that happens, switch to multi-line syntax.
FOR /r %%X IN (*.txt) DO (
ECHO %%X
DEL %%X
)
Placement of ( and ) matters. The round brackets after DO must be placed on the same line, otherwise the batch file will be incorrect.
See if /?|find /V "" for details.