First UMC in Austin, TX uses this blessing during Sunday worship to as a way of praying for all couples. It's designed for use with same-sex couples as well as opposite-sex couples.

NAME and NAME,
as members of the family of [Name of United Methodist Church]
and participants in our shared ministry,
we celebrate that recently you united in marriage,
through the sharing of vows and exchange of rings
before a gathered congregation.

We celebrate the love you share for God,
the life you share together,
and the witness that your covenant relationship
will be to all those around you.

Though we grieve that you were unable to wed
in your own Sanctuary,
by the authority of your appointed pastors,
we claim with hope that God’s blessing knows no limits.

We come today with joy
to pray God’s richest blessings on your life together.

Let us pray:
Most gracious God,
we give you thanks for your tender love
in making us a covenant people
through our Savior Jesus Christ.

Send your blessing upon NAME and NAME,
that they may keep their marriage covenant,
and continue to grow in love and godliness together.
Grant that their love for each other
may reflect the love of Christ for us
and grow from strength to strength
as they faithfully serve you in the world.
Defend them from every enemy.
Lead them into all peace.
Let their love for each other
be a seal upon their hearts,
a mantle about their shoulders,
and a crown upon their heads.

Bless them
in their work and in their companionship;
in their sleeping and in their waking;
in their joys and in their sorrows;
in their lives and in their deaths.

Fill them and us with grace and strength
to be witnesses of your unending love
for all of your beloved children.

Watch over them in the coming years,
and bring them to the feast of eternal life.
All this we ask through Christ our Lord.
Amen.