Without timeshifting/DVR? Who can remember that long ago? Withing the same week or so? Game of Thrones on its current run. A series from beginning to end? Maybe Deadwood?
Oh! I just remembered—the Thundercats revival series!
…which promptly got it’s ass cancelled.
All the ones I can think of were back in the '60s: Batman, Time Tunnel, F Troop, That Girl, Rat Patrol…
Star Trek: TOS was the first one I watched from beginning to end in strip form (five nights a week) back in 1969–70.
All of the others I’ve seen from beginning to end were either stripped as well (e.g., The Sopranos on A&E, after it was on HBO) or the subject of on-line marathons (e.g., Big Bang Theory, the new Dallas).
A lot of other series I’ve loved (e.g., Combat!, The Avengers, Hill Street Blues, St Elsewhere, Cheers!) I can’t honestly claim to have seen in their entirety … yet.
Thanks to PBS, I can also claim to have watched shows like Poldark, The Good Life/Good Neighbors, Danger: UXB, and I, Claudius from beginning to end in something like the manner they were originally aired (in Great Britain).
OMG Poldark! That one I did watch in real time. Must have been before there were football games on Sunday nights. It’s also one of the first shows I rewatched when I figured out how to get Netflix on the teevee.
Another one from the 70’s – Rich Man Poor Man. It was appointment TV for millions. Not as popular as Roots, but damn close. If I remember right, it was on Tuesday nights. I was a cub scout helper, and the scouts met on Tuesday night. But the leader was also a fan, so we always finished with the scout stuff so we could be home by 8 p.m.
I think those shows predated the VCR, but I’m not sure. I know we didn’t have one.
The original Roots I watched when I was living in England. IIRC, it was on once a week, probably Sunday night.
The coming of miniseries changed a lot of things. I remember watching Shogun religiously in the early '80s.
The first guy I knew who actually owned a VCR bought it hot (I kid you not) for a song in '78, I think it was. He was lucky to get it and his Quasar color TV (also hot) out of his apartment in time when he was tipped off that the cops were on their way over. (True story!)
The next time I remember someone owning a VCR was my older brother in '83 or '84. He taped all his favorite shows while he was at work in the evening and watched them after he got home around midnight.
I just have to say those also were two of my most favorite series of all time 
and my future husband and I watched Rich Man Poor Man together when we first got into a relationship. (We also watched Upstairs, Downstairs off and on, it was impossible to watch that all the way through. )
Oh, and Twin Peaks, I watched Twin Peaks all the way through and also recorded it on the ol’ VCR, so I had the whole series to watch again someday. My husband finally took an interest and one weekend watched all the VCR tapes from beginning to end in a marathon viewing session.
Twin Peaks
In real time, Lost.
Via DVD/Netflix binges, Friday Night Lights.
Currently, I haven’t missed an episode of Storage Wars, but that’s likely to change.
I don’t think I ever watched an entire series from premiere to end prior to DVR days. Could never make my schedule that tight.
Real time: Fringe
Huh. I’d have to say never. Even the shows I liked as a kid were catch as catch can. Later, I found a couple of shows to watch (like Cheers, for instance) but I only discovered it in syndication. So, again, catch random episodes here and there.
The closest “must see TV,” as in schedule that evening to watch the show, was The X-Files. I think I kept up with the first 4 seasons but then it got so convoluted and stupid I quit.
These days I hardly watch *any *first-run TV, other than live sports. I wait until a show has enough word-of mouth that I’ll Netflix and binge watch the entire run. I’ve done this with The Sopranos, Lost (sortof regret that one), Deadwood, Buffy, Angel, Breaking Bad (watched final 8 episodes in real time), and probably a few others. Have caught up to Mad Men and will finish it out in real time I guess. Currently have watched 3 seasons of The Wire and will continue to Netflix the rest of the run.
I’ve done it with lots of shows, but I cheat: Most of the shows I like get cancelled in one season or less. Firefly, Journeyman, New Amsterdam, 666 Park Avenue, Golden Boy, Chicago Code, and many more.
I don’t think it’s ever happened. In the past, I found out about a show usually after it had been on a bit. Now, I usually don’t watch shows when they air.
Unless you are counting just going out and binging on every episode. In which case, it would probably be either Futurama (before it was uncanceled) or one of the Star Treks. Lately, I have a tendency to put off watching the last season of a series that I start binging on.
Futurama.