Oilbirds are restricted to South America. They are locally distributed from Guyana, Trinidad and Venezuela in the north and along the Andes south through Colombia, Ecuador, Peru and Bolivia. In Venezuela, the Oilbird occurs in the coastal cordilleras east to Monaguas, at scattered sites in southern Venezuela in Amazonas and Bolívar and in the Andes of northwestern Venezuela (Hilty 2003). It also inhabits northern Brazil on table-top tepui mountains near the Venezuelan border (Bosque 2002). Although generally considered as resident birds, Oilbirds are sometimes short-distance migrants. Post-breeders wander widely even in urban areas (Hilty 2003).
In Venezuela, the elevational range is up to 2000 m north of the Orinoco, and up to 2600 m south of the Orinoco (Hilty 2003). Oilbirds occur up to 3000 m in Colombia (Hilty and Brown 1986); in Ecuador, the primary elevational range is 700-2400 m, but occasionallyit is reported up to 2600 or down to 250 m (Ridgely and Greenfield 2001). In Peru, the primary elevational range is 450-2200 m (Walker et al. 2006, Schulenberg et al. 2007). However some have been reported from a few sites as low as 120 m in eastern Peru, near the Brazil border (Tello et al. 2008).
Wandering individuals have been recorded in Central America and on some Caribbean islands (Bosque 2002). Also occasionally reaches the west slope of the Andes in Peru (Schulenberg et al. 2007). Some individuals have been observed at feeding localities 150 km away from their roosting caves and in Costa Rica, the recordings report individuals 700 km away from their nearest known cave located in Colombia (Thomas 1999, Hilty 2003). Additionally the record of the Oilbird in lowland Amazonia in eastern Peru suggests that there might be Oilbird caves the east of the Rio Ucayali in the Serranía de Contamana or the Serranía del Divisor (Tello et al. 2008).
Much more studies are needed to actually get accurate data of this species distribution. Information about migration and colonies across South and Central America are scarce and therefore much more research in this topic is needed.