A method and apparatus for treating for disposal oil contaminated substrates, such as drill cuttings from drilling with an oil-based mud, by steam distillation. If necessary, the contaminated substrate 10 can be pretreated with an emulsion breaker 14. The contaminated substrate 10 can be treated with steam 16 in a first mixing still 12. The substrate can be optionally treated with a second steam source 20 in a second mixing still 18. The steam provides heat to vaporize the oil, moisture to treat the substrate and water to the reaction mixture. Recoverable constituents in the vapor can be condensed in a vapor collection system 24. The treated substrate 22 is essentially free of oil and can have a controlled water content. The process exhibits low energy consumption, rapid treatment, compact equipment and a high degree of process control.