Bob Bogart has a clarification on my fuzzy Tim McCarver grand slam-cum-3 RBI single recollection:

The Tim McCarver "Grand Slam Single" happened on July 4, 1976, in the first game of a doubleheader at Pittsburgh. In the top of the second inning, with the Phillies' Dick Allen on 3rd base, Jay Johnstone on 2nd, and Garry Maddox on 1st, McCarver hit a fly ball to right, tight to the line. Maddox, thinking Dave Parker might catch the ball, prepared himself to tag up and advance from 1st to 2nd if Parker caught the fly. The ball just made it over the fence for a grand slam, but McCarver wasn't paying attention to Maddox's tagging and passed him at first base. All three base runners scored, and McCarver got 3 RBI's for his efforts on the play. But he only received credit for a single as that was as far as he got before passing a teammate on the bases.
And no, this wasn't in McCarver's last year as he played until 1980.