105.3, The Fan broadcasts all Cowboys games and has good pregame and postgame shows. This is for preseason, postseason and everything in between. You can listen to 105.3 online, just go to their website and hit listen.
The Ticket, during the regular season, does a great pregame show with all their top guys, and a great postgame show with Norm and Donnie. If they are doing preseason, that would be new for them. But I haven't even checked. You can listen to the Ticket on the IHeartRadio app, or on the IHeartRadio website.
If you want one phone app that allows you to listen to both, with thousands of other great stations, get ooTunes. Highly recommended! I live in Florida, and I use it daily to listen to stations back in Texas.
If you want to hear the game broadcasts with Brad Sham, and you're outside the Dallas Cowboys Radio Network, get Sirius XM. You can stream every Cowboys game radio broadcast (and every NFL team's broadcast) through that, through their web portal, through the phone app or through your Sirius XM radio. Costs me $19 a month. Well worth it! The only drawback is that all games through Sirius XM are on a 3-minute delay, so at the start of every game you have to pause the TV for 3 minutes so the radio stream can catch up.