If you mean a bridge in the strict networking sense (simply put, a layer 2 device which passes packets from one interface out of the other), then you should be able to do this like so:
1) Edit both /etc/sysconfig/network-scripts/ifcfg-eth0 and /etc/sysconfig/network-scripts/ifcfg-eth1 to remove any IP address/netmask/gateway configuration and add a specified bridge. It should look something like this:
DEVICE=eth0 (or eth1)
2) Edit a new file, /etc/sysconfig/network-scripts/ifcfg-br0 which contains your IP address information. This should look something like this:
Your IP address is then assigned on the bridge, so should be accessible from either interface. Also packets should be forwarded between the interfaces. If this wasn't what you meant by the question then my apologies, this is how to set up a bridge but it may be that a bridge isn't what you need, the question wasn't 100% clear...