If your library uses the KLAS series use the 800 tag query for single author series and 830 for multi-author series. Here's a query that will find all the BR/DB titles that have a Spanish series:
Advanced search
MARC tag - tag - begins - 800
MARC tag - subfield - begins - L
MARC tag - data - equals - Spanish
BibRec - Klas ID - In - BR*,DB*
To find all the books that have a series heading with another particular foreign language, just swap out the Spanish.
