Methyl tertiary butyl ether (MTBE) and trimethyl orthoformate (TMOF) are potential biofuel ethers and could replace conventional fossil fuels, or act as additives to aid combustion. Laser flash photolysis with laser-induced fluorescence detection of the OH radical has been used to measure the rate coefficients of the OH reaction with these ethers, from 298 K to approximately 740 K. The temperature dependence of the rate coefficients is parametrized as KOH+MTBE(298-680 K) = 9.8 X 10(-13)X (T/298)(2.7) X exp(2500/RT) cm(3) molecule(-1) s(-1) and KOH+TMOF(298-744 K) = 8.0 X 10(-13) X [(T/298)(2.6) + (T/ 298)(-8.1)] X exp[2650/RT] cm(3) molecule(-1) s(-1). The room temperature (298 K) bimolecular rate coefficients were measured as K-OH(+MTBE) = (2.81 +/- 0.32) X 10(-12) cm(3) molecule(-1) s(-1) and KOH+TMOF = (4.65 +/- 0.50) X 10(-12) cm(3) molecule(-1) s(-1) where the errors represent statistical uncertainties at the 2 sigma level in combination with an estimated 10% systematic error. Regeneration of OH radicals was observed for both reactions at higher temperatures in the presence of O-2 via biexponential OH decays, which were observed above 489 K and 568 K, for TMOF and MTBE respectively. The OH yield from MTBE/O-2, between 620 and 700 K, was invariant with the concentration of oxygen (10(15)-10(18) molecules cm(-3)) at (36 +/- 5)%. Mechanisms for OH regeneration from MTBE are briefly discussed and compared with those in the literature and from dimethyl and diethyl ether. The lower OH yield from MTBE, compared to these other ethers, is most likely due to competition with an HO2 formation channel.