As the igniters age from repeated use, they can become weak and longer function properly. Just because they glow, does not mean they are good. If you are experiencing ignition problems, the following link explains a little theory about how these igniters work and how to replace one:
http://www.fixya.com/support/r3575727-replacing_an_oven_igniter_on_a_gas_rangeThe burner manifolds in the oven each use a glow bar or electrode type igniter with a gas safety valve to ignite. Both oven manifolds are controlled by the Electronic Oven Control (EOC) board, which is your clock/timer on the control panel. If the surface burners work, but the oven does not, the problem is usually not a gas related issue. It can be a control board issue, but is usually a weak or failed oven igniter.
Replacement parts (if required) can be purchased at any of the following websites:
searspartsdirect.com
pcappliancerepair.com
appliancepartspros.com
repairclinic.com
Prices vary between these sites, so shop and compare. The first three sites listed also offer helpful exploded view diagrams to help you locate and properly identify the parts you need.
If you have any questions please post back with a complete MODEL NUMBER and let me know. I hope this helps you.