Jeffrey A. Leon

Jeffrey A. Leon

Highland Park, Illinois

Jeff joined Quantum Legal on January 1, 2009 as a partner, where he has headed the firm’s antitrust and competition practice.  Jeff has devoted the entirety of his more than two-decade long legal career to litigating complex commercial cases.  Jeff spent eighteen years practicing at some of the nation’s largest law firms where his practice focused on antitrust litigation and counseling and the defense of class action lawsuits. Jeff was an associate at Kirkland and Ellis (from1991-1996), an associate (from 1996-2000) and a partner (from 2001-2008) at Winston & Strawn and a partner at Ungaretti & Harris (from 2007-2008) until he joined Quantum Legal.

At Quantum Legal, Jeff has put his experience to work pursuing class action lawsuits on behalf of aggrieved consumers and businesses, while continuing to serve select corporate clients on a fee-for-service or contingent fee basis.

While at Quantum Legal, Jeff has served as co-lead counsel or as an executive committee member in lawsuits that have delivered hundreds of millions of dollars in benefits to consumers who were aggrieved by the conduct of companies as diverse as J.P. Morgan Chase Bank N.A., The Western Union Company, Sprint, AT&T, Verizon, LG, Allstate, and Nationwide.

Jeff also continues to represent companies on a contingent or fee for service basis in complex commercial litigation, with a special emphasis in representing alternative energy companies in warranty litigation, lender disputes and construction litigation.

Jeff is also a frequent appellate advocate.  Since 2011 Jeff has argued five federal appellate court appeals and has been the lead drafter of numerous other appeal briefs submitted without argument.

Because Jeff has spent a significant amount of his legal career representing both plaintiffs and defendants, he has a unique perspective which guides his litigation strategy and assists clients in ultimately obtaining relief short of trial.  However, if a client’s case must go to trial, Jeff has the necessary experience in trying bet-the company cases.  Jeff was the co-lead trial lawyer defending ITW Corporation in a two and one-half month federal court jury trial against claims it had engaged in a conspiracy to fix the prices of high pressure laminate, which ended in a complete defense verdict in favor of his client. The class in that case was seeking $1.3 billion in damages. Jeff was also the lead lawyer defending Chicago Bridge & Iron in a three-month bench trial at the Federal Trade Commission against a challenge to its acquisition of Pitt-Des Moines, Inc.  Finally, Jeff defended Yukon Fuel in a contested consent decree proceeding and temporary restraining order hearing concerning its merger with its largest competitor, defeating challenges to the merger in both proceedings.
Jeff also has a dedication to seeking in some small way to right some of the wrongs that have plagued victims of genocidal actions.  Thus, Jeff is currently co-lead counsel in litigation against the Hungarian national bank and railroad on behalf of Holocaust victims and their families whose seized assets have not, even to this day, been returned to them. Jeff is also co-lead counsel on behalf of victims of the Krajina massacre in Croatia in litigation against a U.S. based military contractor.

Jeff is in high demand as a frequent speaker.  He for the past several years has served as a co-chair of the American Association’s National Class Action Institute where he has moderated and spoken on a variety of panels.  He has spoken on panels in recent years for numerous other conferences and for web-based continuing legal education programs, and he participated in a panel in a conference sponsored by Navigant Economics where he discussed the legal use of econometric models.  Jeff also has in the past lectured on antitrust law at the Kellogg School of Business at Northwestern and he has published several articles on antitrust law including DISAGGREGATION OF ECONOMIST LIABILITY TESTIMONY IN SECTION ONE LITIGATION, ABA Section of Antitrust Law Economics Committee Newsletter and THE EVIDENTIARY ROLE OF ANTITRUST COMPLIANCE POLICIES IN SECTION ONE CIVIL LITIGATION, ABA Sherman Act Section One Committee Newsletter.

Jeff is a 1991 summa cum laude graduate of the Indiana University School of Law where he was third in his class, editor of the Indiana Law Journal, champion of the Sherman Minton Moot court competition and a member of the Order Of The Coif. Jeff graduated cum laude from the University of Redlands in 1987 with degrees in political science and history. Jeff was a championship debater at Redlands, and was selected as the fifth most outstanding individual speaker at the 1987 National Debate Tournament.

Jeff may be contacted at any of the following:

Direct Ext.:      847-433-4500 Ext. 2604
Firm Phone:     847-433-4500
Firm Fax:         847-433-2500

Litigation Percentage

  • 100% of Practice Devoted to Litigation

Bar Admissions

  • Illinois, 1991
  • U.S. District Court Northern District of Illinois, 1991


  • Indiana University School of Law, Bloomington, Indiana
    • J.D. summa cum laude - 1991
    • Honors: Order of the Coif
    • Honors: Winner of the 1990 Sherman Minton Moot Court
    • Law Journal: Indiana Law Journal, Managing Editor, 1990 - 1991
    • Law Journal: Indiana Law Journal, 1989 - 1991
  • University of Redlands, Redlands, California
    • B.A. cum laude - 1991
    • Major: Political Science and History

Past Employment Positions

  • Kirkland & Ellis, Associate, 1991 - 1996
  • Winston & Strawn, Associate , 1996 - 2000
  • Winston & Strawn, Partner, 2000 - 2007
  • Ungaretti & Harris, Partner, 2007 - 2008


  • Alpha Gamma Nu