You may have a bad igniter on the oven manifold. The broiler and oven use separate igniters. So, if the broiler works, you don't have a gas problem. No ignition is most commonly attributed to an oven igniter that is going bad. As these igniters age, they become weak and require replacement. The following link explains some theory behind how they work and how to replace one:http://www.fixya.com/support/r3575727-replacing_an_oven_igniter_on_a_gas_range
Replacements parts can be purchased at any of the following web sites:
Prices vary, so shop and compare.
NOTE: If the replacement igniter comes with a connector plug that does not match the one on your range, you will be instructed to cut the old connector plug off and splice the wires together using a set of ceramic wire lugs that are included in the replacement kit. DO NOT attempt to use standard wires lugs. They will melt due to the extreme heat in an oven. The ceramic lugs and the wires on the igniter are heat resistant.
NOTE: If BOTH oven features do not work, these features are controlled by the Electronic Oven Control (EOC) board. This is the clock/timer assembly on the operator console. It is possible for the control board to fail and disable both oven features.
If you have any questions about this repair, please let me know. I hope this helps you.