The "Desperate Housewives" star worked the drive-thru Tuesday at the restaurant to help kick off the Father's Day Frosty Weekend.
The event donates 50 cents for every Frosty sold to the Dave Thomas Foundation for Adoption and its signature program Wendy's Wonderful Kids.
Longoria Parker worked at Wendy's from 1991 to 1994, the Corpus Christi Caller-Times reported in its online edition.