We report the design, construction and performance of a versatile substrate heater that meets the severe design constraints of heating substrates to high temperatures (less-than-or-equal-to 900-degrees-C) in relatively high pressures (hundreds of Torr) of oxidizing gases. The heater has been used to heat substrates by both thermal conduction via a conductive high temperature cement and by direct radiation. In particular, the production of high-quality YBa2Cu3O7-delta thin films grown on radiatively heated LaAlO3 substrates is demonstrated using the pulsed laser deposition (PLD) technique.