She was elected Whip for the Republican Caucus after her first term, and in 2005 became the first woman to serve as Speaker Pro Tempore, the second highest position in the House.

Winchester co-owned and operated American Dusting Company and Chickasha Flying Service from 1976 to 1989, after which she worked as a coordinator for Adult Training and Development at Canadian Valley Technology Center.

During her time in office, she served as Chair of the Banking Subcommittee of the Economic Development and Financial Services Committee.

In 2005 Winchester became the first female and only the second Republican to serve as Speaker Pro Tempore, the second highest position in the House, since statehood.

[6] In 2023, she led the presidential search advisory committee for the University of Central Oklahoma and supported the hiring of her Todd Lamb.