CH₃I-oxygen line-broadening coefficients at 296 K are calculated for the ^RR, ^PR, ^RP, ^PP, ^RQ and ^PQ sub-branches of the ν₆ band in a wide range of rotational quantum numbers (0≤J≤70, K≤20 by a semi-classical and a semi-empirical methods. The computed values compare very favourably with the available experimental data and therefore can be safely employed as estimates of broadening coefficients missing in databases for high J and K. The theoretical data for CH₃I-O₂ are further combined with the previously calculated room-temperature CH₃I-N₂ line-broadening coefficients to obtain the air-broadening values required for atmospheric applications. The calculated results demonstrate an excellent consistency with both existing sets of CH₃I-air measurements. As the vibrational dependence of CH₃I oxygen-broadening coefficients is shown to be small, similarly to the nitrogen-broadening case, the CH₃I-O₂ and CH₃I-air line-broadening coefficients calculated for the ν₆ fundamental can be used for other perpendicular and parallel bands.