Okla. Stat. tit. 12A, § 12A-2-612: "Installment Contract"; Breach

(1) An "installment contract" is one which requires or

authorizes the delivery of goods in separate lots to be separately

accepted, even though the contract contains a clause "each delivery

is a separate contract" or its equivalent.

(2) The buyer may reject any installment which is nonconforming

if the nonconformity substantially impairs the value of that

installment and cannot be cured or if the nonconformity is a defect

in the required documents; but if the nonconformity does not fall

within subsection (3) and the seller gives adequate assurance of its

cure the buyer must accept that installment.

(3) Whenever nonconformity or default with respect to one or

more installments substantially impairs the value of the whole

contract there is a breach of the whole. But the aggrieved party

reinstates the contract if he accepts a nonconforming installment

without seasonably notifying of cancellation or if he brings an

action with respect only to past installments or demands performance

as to future installments.