Born in Germantown, she graduated from Germantown Friends School in 1953 and attended Wellesley College before leaving in 1956 to marry.
She earned a bachelor's degree in sociology at the University of Pennsylvania in 1976 and a master's in social work at Bryn Mawr College in 1980.
Mrs. Fosnocht was president of the parent-teacher organization at the Green Tree Elementary School in Willistown in the 1960s and 1970s, her husband said.
A field hockey player in high school, she founded the girls' hockey team at Green Tree, which she coached from 1967 to 1977.
Twice a week in the 1990s, she was a classroom aide in math at Sugartown Elementary School, where her husband was an English aide.
Mrs. Fosnocht and her husband taught Sunday school classes at Good Samaritan Episcopal Church in Paoli in the 1960s and 1970s.
She was a member of the choir and the vestry at St. Francis-in-the-Fields Church in Malvern in the 2000s, working as rector's warden there from 2002 to 2007.
Mrs. Fosnocht was a member of the Paoli Hospital Auxiliary and both the Merion Cricket Club and the Waynesborough Country Club, where she played tennis.
Besides her husband, Mrs. Fosnocht is survived by sons Thomas A. Jr. and John; daughters Joan Orr, Mary Albrecht, and Rebecca Misangyi; a brother; two sisters; and 15 grandchildren.
A visitation was set for 10 a.m. Thursday, Oct. 18, at St. Francis-in-the-Fields Church, 689 Sugartown Rd., Malvern, before an 11 a.m. funeral service there.
A reception was set from 1 to 4 p.m. at Waynesborough Country Club.
Contact Walter F. Naedele at 215-854-5607 or firstname.lastname@example.org.