1 EXHIBIT 23a CONSENT OF VAVRINEK, TRINE, DAY & CO. PAGE 42 OF 43 2 [VAVRINEK, TRINE, DAY, & CO. LETTERHEAD] CONSENT OF INDEPENDENT CERTIFIED PUBLIC ACCOUNTANTS To: Heritage Oaks Bancorp We consent to the incorporation of our report dated February 8, 1996, on the consolidated financial statements of Heritage Oaks Bancorp as of December 31, 1995 and 1994, and for each of the three years in the period ended December 31, 1995 included in its Registration Statement on Form S-8 for the year ended December 31, 1995. /s/ VAVRINEK, TRINE, DAY & CO. - ------------------------------ VAVRINEK, TRINE, DAY & CO. Certified Public Accountants Rancho Cucamonga, California