Specialized regulatory T (Treg) cells accumulate and perform homeostatic and regenerative functions in nonlymphoid tissues. Whether common precursors for nonlymphoid-tissue Treg cells exist and how they differentiate remain elusive. Using transcription factor nuclear factor, interleukin 3 regulated (Nfil3) reporter mice and single-cell RNA-sequencing (scRNA-seq), we identified two precursor stages of interleukin 33 (IL-33) receptor ST2-expressing nonlymphoid tissue Treg cells, which resided in the spleen and lymph nodes. Global chromatin profiling of nonlymphoid tissue Treg cells and the two precursor stages revealed a stepwise acquisition of chromatin accessibility and reprogramming toward the nonlymphoid-tissue Treg cell phenotype. Mechanistically, we identified and validated the transcription factor Batf as the driver of the molecular tissue program in the precursors. Understanding this tissue development program will help to harness regenerative properties of tissue Treg cells for therapy. Display omitted •Two precursor stages of ST2+ nonlymphoid-tissue Tregs are evident in the spleen and LNs•Precursor stages are defined by differential expression of Nfil3, PD1, and Klrg1•Chromatin accessibility and scRNA-seq suggests a stepwise precursor reprogramming•Batf drives the molecular tissue program in the precursors Whether a common precursor exists for nonlymphoid-tissue Treg cells is unclear. Delacher et al. identify two precursor stages for tissue-resident ST2+ Treg cells. These precursors undergo a stepwise reprogramming in the lymphoid organs toward the nonlymphoid-tissue Treg cell phenotype. Chromatin accessibility profiling identified Batf as a key driver of the tissue program in the progenitor cells.