I found the wiring diagram (in a pocket on the back of the oven) - but
it's a bit beyond my ken. However, last night I spent some time
looking for behavior patterns. What I found was that once the oven
reached temperature, the glowbar and burner would go off as expected.
Some time after that, (presumably when the oven needed warming to stay
at temperature) one of 3 things would happen: 1: I the glowbar would
start to glow, then after a short time stop glowing - no gas. 2: the
glowbar would glow, then the gas burner would come on and then go off
again almost immediately. 3: The glowbar would glow then the gas
burner would come on and stay on for a while, heating up the oven
(proper functioning).

So it seems likely that the problem is with the glow bar (or possibly
some logic chip) - but it seems to be intermittent. I'll test it with
an ohm meter, but that my be inconclusive. It looks like the glow bar
for the broiler is the same part, so I'll see if I can swap them for
now and see if that fixes the oven problem. I tested the broiler and
it seemed to be functioning properly (#3 above).

Thanks for your inputs.