Steven Barker joined Cornerstone as a Principal in our Oklahoma office in November 2025.

Prior to Cornerstone he served as Assistant Municipal Counselor for the City of Oklahoma City. In this role, he represented the city in eminent domain and land use matters, advised the City Manager's Office and Planning Department and supported key strategic initiatives, including securing a 25-year lease agreement with the Oklahoma City Thunder.

Previously, Steven served as General Counsel at Coop Ale Works, providing nationwide regulatory guidance to support product distribution. In this role, he managed all federal and state compliance, negotiated agreements with distributors and oversaw the company's licensing portfolio.

Earlier in his career, Steven worked with the Oklahoma Alcoholic Beverage Laws Enforcement Commission, where he held leadership roles as Deputy Director and General Counsel. He has also served as an Assistant Attorney General in the Oklahoma Attorney General's Office and as Assistant General Counsel with the Oklahoma Tax Commission. Steven currently serves as Chief Municipal Judge for the City of Warr Acres, where he presides over arraignment, juvenile and trial dockets.

Steven holds a Juris Doctor from Oklahoma City University School of Law and a Bachelor of Arts in Political Science from Pittsburg State University.

Lauren McCay serves as a Senior Associate in Cornerstone's Oklahoma City office, assisting the firm's government relations team with client service activities including conducting research and providing updates on state legislative matters and diverse regulatory issues.

Lauren comes to Cornerstone from Lilly & Company where she led the firm's highly successful fundraising effort in Oklahoma as an Account Executive. She was responsible for executing numerous fundraisers and meeting fundraising goals for current federal legislators and those seeking office in the U.S House and Senate.

Before joining Lilly & Company, Lauren served as a Congressional Intern for Representative Stephanie Bice (R-OK) where she managed and answered constituent inquiries while also supporting staff by taking initiative on various district office projects and case work.

Lauren received her Bachelor of Science in political science from the University of Oklahoma.

Mark Yates joined Cornerstone in July 2021 as a principal in the firm's Oklahoma City office. His experience in public policy includes working with various industries through statewide campaigns, legislative engagement, media relations, and public speaking. Mark has been successful navigating complex and challenging initiatives on behalf of the clean energy and agriculture industries.

Mark previously served as vice president at Advanced Power Alliance (APA) where he represented leading domestic and international companies in the renewable energy sector. While in this role, he managed the association's regional public policy strategy, communications strategy, and membership recruitment efforts. Mark served a major role in shaping legislative and regulatory policy within the most important energy region in the country.

Prior to APA, Mark worked at the Oklahoma Farm Bureau, where he led membership recruitment initiatives, mobilized a statewide grassroots campaign, and lobbied for rural issues on behalf of the nearly 90,000 farmers and ranchers.

Before his time with the Farm Bureau, Mark was a professional educator in the Oklahoma public school system for 11 years. Along with his teaching experience, Mark also had administrative experience serving as a federal programs director for Plainview Public Schools in Ardmore, OK.

Mark is a graduate of East Central University in Ada, OK and holds a bachelor's degree in History and master's in Secondary Administration. Mark and his wife Stacy reside in Edmond, OK where they are active in their community and have two children, Londyn and Steele.