Okla. Stat. tit. 68 § 3140
To defeat the deed, the person desiring to set the same aside and recover the land, or to resist the recovery of possession by the holder of the deed, in addition to showing clearly the entire failure to do some one or all the things of which the tax deed is made presumptive evidence, must show that he or the person under whom he claims had the right to redeem the land from tax sale at the time the deed was made, and must, when his action to set aside the tax deed is brought, or a defense to a recovery of possession is pleaded, tender in open court for the use of the holder of the tax deed, all taxes, penalties, interests and costs, which the party seeking to redeem would be bound to pay if he was then redeeming the land from tax sale, and on failure so to do, his action or defense, as the case may be, shall be dismissed. The rule that tax proceedings are to be strictly construed as against the tax purchaser, shall not apply to proceedings under this article, but in all courts its provisions shall be liberally construed, to the end that its provisions and all proceedings thereunder shall be sustained.
Okla. Stat. tit. 68, § 3140