With Manning and Romo watching in uniform from the sidelines, Osweiler played three efficient quarters, completing nine of 13 for 190 yards without an interception.
Romo's backup, Weeden, came out before halftime of his second ragged game in four preseason outings. He was 6 of 12 for 75 yards with an interception that set up Denver's first touchdown.
The Cowboys (0-4) didn't make the playoffs in three of their other four winless preseasons and are trying to avoid matching a club record with a fifth straight year of missing the postseason.
Ware had a long pregame chat on the field with Jason Witten, the Dallas tight end who interrupted Ware's conference call with reporters this week for some playful trash talk.
Anderson got the heaviest load with 14 carries for 33 yards and a 1-yard touchdown set up by Osweiler's longest completion, a 34-yarder to a leaping Andre Caldwell near the goal line.
Weeden led a 74-yard drive to a field goal, but was off the mark on several throws and had just one first down in three other possessions.
The Cowboys changed their plan to get their free agent tackle his first preseason action before the opener, taking the safe route instead with his groin injury. Melton hasn't played since a torn knee ligament ended his final season in Chicago in Week 3 last year.
Copyright 2014 by The Associated Press