What is WELS' position on transubstantiation? Bread and wine become the body and blood of Christ or, they are the body and blood because of God's omnipresence?
You will find these statements in This We Believe: a statement of belief of WELS:
“We believe that all who join in the Sacrament of the Lord’s Supper receive the true body and blood of Christ in, with, and under the bread and wine (1 Corinthians 10:16). This is true because, when the Lord instituted this sacrament, he said, ‘This is my body. This is my blood of the covenant, which is poured out for many for the forgiveness of sins’ (Matthew 26:26,28). We believe that Christ’s words of institution cause the real presence—not any human action. As believers receive his body and blood, they also receive the forgiveness of sins (Matthew 26:28) and the comfort and assurance that they are truly his own. Unbelievers also receive Christ’s body and blood, but to their judgment (1 Corinthians 11:29).
“We reject the doctrine of transubstantiation, which teaches that the substance of the bread and wine are changed entirely into the body and blood of Christ. Scripture teaches that all communicants receive both the bread and wine and the body and blood of Christ (1 Corinthians 10:16).”