Can Spouse Endorse Check if for Joint Account?

Actually, under UCC section 4-205 (check your state's UCC enactments to ensure it's there and how it's worded), if the check is payable jointly (not in the alternative) and is to be deposited to a joint account in the name of the check payees, neither payee would have to endorse the check; the bank could accept it for deposit without endorsement and still be protected with charge-back rights and the rights of a holder in due course.

You should also check the wording of the deposit agreement covering the account. Many newer deposit agreements include reciprocal powers of attorney between the joint owners allowing either of the owners to endorse checks for the other joint owner for the purpose of depositing them.