The olfactory epithelium (OE) is a neurosensory organ required for the sense of smell. Turbinates, bony projections from the nasal cavity wall, increase the surface area within the nasal cavity lined by the OE. Here, we use engineered fibroblast growth factor 20 (Fgf20) knockin alleles to identify a population of OE progenitor cells that expand horizontally during development to populate all lineages of the mature OE. We show that these Fgf20-positive epithelium-spanning progenitor (FEP) cells are responsive to Wnt/β-Catenin signaling. Wnt signaling suppresses FEP cell differentiation into OE basal progenitors and their progeny and positively regulates Fgf20 expression. We further show that FGF20 signals to the underlying mesenchyme to regulate the growth of turbinates. These studies thus identify a population of OE progenitor cells that function to scale OE surface area with the underlying turbinates. Mechanisms regulating olfactory epithelium expansion and turbinate growth are poorly understood. In this issue of Developmental Cell, Yang et al. show that an Fgf20-expressing progenitor (FEP) expands the olfactory epithelium and regulates turbinate growth via FGF20. Furthermore, Wnt/β-Catenin signaling acts as a master regulator of these two processes. © 2018 Elsevier Inc.