From 1990 (when the NFL began scheduling seasons with bye weeks) to 2010, the Cowboys have a 15-5 record following their bye week. Their record the last three seasons after the bye is 0-3. The Cowboys are 0-2 all-time when playing the Giants following their bye week.
Another interesting number is the Cowboys record the week before their bye week. From 1990-2010 their record prior to their bye week is 16-4. Their record the last three seasons 1-2.
Some more fun with bye week numbers:
The Cowboys record against the NFC the week after their bye is 13-4.
The Cowboys record against the AFC the week following their bye is 2-4.
The Cowboys record against the NFC East the week after their bye, 9-3
The Cowboys have faced the Eagles five times after their bye week, the most of any opponent. The Cowboys record in those meetings 4-1.