This article explores portions of the Thessalonian correspondence through a missional lens, focusing on its depiction of the church's election, the mode of the church's participation in the missio Dei as it lives out its election, and the particular sort of missional understanding of the Trinitarian God this reading suggests. This exploration is framed by a conversation with two recent proposals that revise (McDonald), or interact heavily with (Flett), Barth's Christological redefinition of the doctrine of election. The article assumes that Barth was right to redefine the doctrine of election Christologically and that doing so must factor into how one articulates an ontology of the Triune God. As a starting point, it also utilizes McDonald's basic twofold representational dynamic of election, namely, election as the representation of God to others and others to God. However, the article's reading of the Thessalonian correspondence suggests a different understanding of the elect's participation in the missio Dei than is articulated by either Flett or McDonald. Features of these letters suggest that the elect's participation in the missio Dei is best understood as ontic participation in the Triune God's actions/being, that is, as a Spirit-generated representing of God's very self to others and others to God. The article concludes with an attempt to ground this understanding of the elect's participation in the missio Dei in an ontology of election that gives the Spirit a more prominent place in the Triune God's unfolding life with God's elect people.