EXHIBIT 23.15 CONSENT OF UBS WARBURG LLC We hereby consent to the use of our opinion letter dated August 13, 2001 to the Board of Directors of Devon Energy Corporation ("Devon") included as Annex F to the Joint Proxy Statement/Prospectus which forms a part of the Registration Statement on Form S-4 dated October 29, 2001 relating to the proposed merger of Devon and Mitchell Energy & Development Corp. and references to such opinion in such Joint Proxy Statement/Prospectus. In giving such consent, we do not admit that we come within the category of persons whose consent is required under Section 7 of the Securities Act of 1933, as amended, or the rules and regulations of the Securities and Exchange Commission thereunder, nor do we thereby admit that we are experts with respect to any part of such Registration Statement within the meaning of the term "Experts" as used in the Securities Act of 1933, as amended, or the rules and regulations of the Securities and Exchange Commission thereunder. UBS WARBURG LLC By: /s/ JAMES BRENNAN --------------------- James Brennan Managing Director New York, New York October 29, 2001