"MARCUS WELBY, M.D." was the network's highest-rated dramatic series during the 1971-'72 season [Tuesdays, 10-11pm(et)]. That's one reason why ABC didn't want to "break up" their Tuesday night schedule {7:30 THE MOD SQUAD/8:30 THE MOVIE OF THE WEEK/10:00 MARCUS WELBY}, and received a special waiver from the FCC that fall to keep that line-up intact, while starting their prime-time schedules at 8pm on other evenings, as the other networks were forced to do. In return, though, 8:30-9 on Mondays (right after "NANNY AND THE PROFSSOR") was returned to ABC affiliates for local programming for a brief period, although that experiment didn't work, and the time returned to the network in January 1972. They finally started their Tuesday night schedule at 8 in the fall of '72...