You can't filter your way to this. No database stores "who this agency's clients are." So stop looking for agencies.
Start with the brands instead and work backwards.
Nation's Restaurant News publishes a Top 500 chains list every year, plus a 100 Under 100 for the smaller ones. That's your whole universe. A few hundred names, and it's already sitting there.
Now find who does their marketing. Three free places:
1. Award sites. The Shorty Awards list the agency and the client in the same line — literally "Agency: X; Client: Y." They have food and hospitality categories, and winners going back to 2009. Effie does the same thing. That's a decade of agency-client pairs, free.
2. News. When a chain hires a new agency, AdAge, AdWeek and NRN write about it. Brand named, agency named, dated.
3. The agency's own site. Client logos on their work page. Use this to confirm, not to find.
One more angle worth a look: the big chains have thousands of franchisees who hire their own local agencies. Whole different set of shops, way less picked over.
Google Maps gives you restaurants, not their agencies
