Broadcast network ION Television, which began airing M*A*S*H in September of 2008, no longer airs the series on a regular basis, using it instead as weekend filler. One episode aired this afternoon from 1-1:30PM and, according to TV Guide listings, it will air again later month on Saturday, June 18th and Saturday, June 25th at 2:30AM.
However, ION Life — a specialty digital network “dedicated to promoting active lifestyles and wellness” available on ION Television affiliates as a digital subchannel — does appear to be regularly airing the series, at least this month. Again, based on TV Guide listings, it appears the series is being shown in blocks from 6-11PM on Saturdays and Sundays (although on Sunday, June 19th it only airs from 6-8:30PM).
ION Life can also be found on certain cable systems. Check your local listings to see if you receive ION Life. I know I don’t. Why exactly M*A*S*H is being shown on a network focused on health and wellness is a good question.