"Is there a biblical perspective on oral sex?
The central principle from which you want to look at any sexual act in a marriage is:
Does it edify, bless and bring pleasure to your spouse in a way that contributes to their redeemed nature, according to the design of God for human sexual behavior?
Anal sex, therefore, would be always prohibited because it damages the persons body and because it mocks the divine intent of sexuality revealed in the Scriptures and in the way God designed the human body.
Using the same guiding principle, oral sex also would be prohibited if one of the spouses found it unpleasant.
Some spouses who find it unpleasant will pretend to find pleasure in that act, (especially those whose identities are centered in their spouse rather than God), out of a need to please their partner at any cost or as a result of other more obvious psychologically and/or physically coercive measures imposed by their spouse. In such cases, the behavior would therefore also be prohibited.
I personally cannot imagine a wife finding it pleasant (when taken to completion) and suspect that most who say they do have had their affections negatively influenced by abuse, unhealthy idolatry of their spouse, the ongoing affects of a previously promiscuous life, sexual abuse or other similar influences by which the mind and heart has gotten twisted.
As for a wife performing the act short of completion as a prelude to normal intercourse, that is indeed more difficult to call. It may be, that since the sexual parts of the human body were designed to merge in one obvious place, that oral sex is an abrogation of the divine intent for the sex act. On the other hand, it may be that since pleasure-giving is a legitimate part of the act (powerfully built right into it) that oral sex under the prime directive given above may not be against God's intent for the marriage bed.
Since it is one of more difficult sexual behaviors to call, I believe that ultimately the married couple should take the question directly to God, and taking great care not to allow personal prejudice sway their thoughts, receive their answer from Him.
One thing is certain, however, that if one partner does not want to engage in it, then to force or coerce the other to participate would be to go against the entire unitive purpose of God's intent for human sexuality. Oral sex is most definately not necessary and does not contribute to the primary purpose of human sexual behavior, which is to be fruitful and multiply. It therefore is dispensible in the achievement of the "One Flesh" union.
David Kyle Foster