<<Disclaimer: Verify this information before applying it to your situation.>>
 
I used to get a very strong reaction to McDonald's meat patties (and
nothing else but lettuce and tomato, neither of which bother me).   At
Wendy's ("all beef burgers") the same thing (meat patty, lettuce & tomato)
gave me no (discernible) problems whatsoever.
 
Note:  All of this is based on experience over eight years ago.  I have
since resorted to always bringing my own, having become fed up with all of
the numerous hidden traps.     More trouble, but you know you're safe.   In
my case, my health improved markedly when I began that policy (and I had
never deliberately ingested any grain product whatsoever and had
religiously avoided all commercially processed foods for years before
then.)     Ironically, it now seems far simpler to me to just bring my own
than all of the numerous previous hassles and worries involved in checking
everything out.   When eating out with a group, just explain that you're
very "allergic" and offer to pay a cover charge.   Allergic they
understand.