Check to see if the broil burner works. This will verify that you are getting gas to the oven portion of the range.
If the broiler does not work, I recommend that you check the service gas shut-off valve on the regulator as shown in the first image below. That component will shut off the gas supply to the oven even though the stove top burners will still work.
If the broiler works, I recommend that you pull the bottom panel of the oven and check the igniter on that bake burner to see if it glows. The theory of operation for that oven burner ignition system is shown in the second image. Here is a link for a video that explains that ignition process:
Oven Burner Gas Ignition Operation
. If that igniter is glowing but the burner will not light, then it is likely that you will need to replace that igniter. You can order that part from the
website. Use the full model number of your range to access the parts list diagram for your range and order the correct part. Be sure that you
unplug the range
and shut off the gas supply before accessing and replacing that igniter. Here is a video that shows how to replace that igniter:
Bake Igniter Replacement
This information should help you fix this problem on your own. If you need more assistance, reply with additional details and the full model number of your range.
If you get to the point where you need to have a service technician diagnose and repair this oven heating failure, you can schedule service through this link:
Sears Home Services