Antigen receptor gene assembly is governed by transcriptional promoters and enhancers that communicate over large distances and modulate chromatin accessibility to V(D)J recombinase. The precise role of these cis-acting elements in opening chromatin at recombinase targets and the mechanisms underlying their crosstalk remain unclear. We show that the TCRβ enhancer (Eβ) directs long-range chromatin opening over both DβJβ clusters. Strikingly, chromatin associated with the Dβ1 gene segment is refractory to Eβ-mediated opening. Accessibility at Dβ1 is accompanied by the formation of a stable holocomplex between a Dβ-proximal promoter and Eβ. These findings indicate a stepwise process for Dβ → Jβ recombination that relies on distinct aspects of Eβ activity: an intrinsic function that directs general chromatin opening and a cooperative function that facilitates the assembly of a promoter/enhancer holocomplex, unmasks the Dβ1 gene segment, and triggers TCRβ gene assembly.