I have an 8 year old Frigidaire stove whose oven came on one night and would not turn off.

Pushing the clear/off button has no effect. Also tried setting oven timer and that does not turn it off. It is the bottom oven element only, and it goes red hot. The oven need to be unplugged or oven element stays on high.

I took off the rear panel and looked at connections, all are fine. Also looked at temperature probe and it looked okay. All other functions on the stove operate properly (burners, broiler, clock and timer)

Is this a failed Electronic Oven Control? Any other diagnostics I can try before ordering an expensive electronic part that will probably not be returnable if that unit is not the culprit?

Here are your parts
Replacement parts for FRIGIDAIRE FEFL77ASF Frigidaire/electric Range | AppliancePartsPros.com

Here is the wiring diagram
http://manuals.frigidaire.com/prodinfo_pdf/Springfield/316255141.pdf

You basically have done the troubleshooting.
The only other way for the element to stay on all the time is if it's were to short to the L1 wire. Which is very unlikely.

You may want to order from AppliancePartsPros as long as you have done some troubleshooting they will allow you to return the part if it does not fix your problem.
See their return policy.

Control Board is Item F20 in Section 1.
If the Overlay is the stick on type you will probably also require it (Item 20A in Section 1)