Smith ran for a pair of scores and safety Darren Woodson returned an interception 94 yards for a touchdown as the Cowboys clinched their third straight NFC East title with a 31-19 victory over the reeling Philadelphia Eagles.
The Pittsburgh Steelers also clinched a playoff berth, but they did it with the help of rookie running back Bam Morris.
The Cowboys (11-2) have won 14 straight games over NFC East opponents, including four in a row over the Eagles, who have lost their last four games to fall to 7-6.
Dallas has won its last three games behind three different quarterbacks. In a win over the Washington Redskins three weeks ago, starter Troy Aikman and backup Rodney Peete were both injured. Third-stringer Jason Garrett was the hero in a Thanksgiving win over Green Bay and Peete was behind center today as Aikman remains sidelined.
Peete had a 19-yard scoring pass to Michael Irvin early in the game and tossed a pair of long passes to set up both of Smith's scoring runs.
Morris, starting in place of injured Barry Foster, ran for 108 yards and two touchdowns, and Neil O'Donnell threw for two scores in his return to the lineup as the Steelers pounded the Cincinnati Bengals, 38-15, to become the first AFC team to secure a playoff berth.
Pittsburgh (10-3), which has made the playoffs in each of its three seasons under head coach Bill Cowher, has won five straight games and eight of nine to take a one-game lead over the Cleveland Browns (9-4), who lost, 16-13, to the New York Giants.
Just when all the skeptics left the Buffalo Bills for dead, again, they caem back from a 10-point deficit with a 35-points second half in a 42-31 win over the Miami Dolphins.
Jim Kelly was 18-of-28 for 299 yards and four touchdowns, including a 72-yarder to Don Beebe and an 83-yarder to Andre Reed. Reed had two scores in the game and moved into third place on the all-time recpetions list with 647.
Buffalo is 7-6 and tied for second place in the AFC East with the New England Patriots. The Dolphins hold a slim one-game lead at 8-5 and could have virtually locked up the division and knocked the Bills into a last-place tie with a victory.
The New York Jets, who were playing for the lead in the AFC East just a week ago, fell into the division basement after losing to the Patriots, 24-13.
Ricky Reynolds scored on an 11-yard interception return in the third quarter that put New England (7-6) ahead for good. The Patriots, who have won four straight games, kept themselves in contention for a playoff berth.
The lone bright spot for the Jets came when wide receiver Art Monk tied Steve Largent's all-time NFL record of 177 straight games with at least one reception.
The Jets are now tied for the bottom spot in the division, because the Indianapolis Colts defeated the Seattle Seahawks, 31-19. Don Majkowski ran for a touchdown and threw for another as the Colts (6-7) rebounded from a 10-point deficit and kept their slim playoff hopes alive.
The Seahawks (5-8), virtually eliminated from the wild card race, completed a tragic week. Chris Warren, Seattle's leading rusher, played despite broken ribs suffered in a mid-week car accident that paralyzed defensive tackle Mike Frier and injured rookie running back Lamar Smith.
The San Diego Chargers can capture their second AFC West Division title with a win over the Los Angeles Raiders on Monday night. The Chargers moved into that position when the Denver Broncos edged the Kansas City Chiefs, 20-17, in overtime today.
The Chargers (9-3) have won three of the last four meetings against the Raiders (6-6), who need a win to remain in the playoff hunt. Los Angeles quarterback Jeff Hostetler is questionable for Monday night's game after suffering a concussion in last week's 21-3 loss to Pittsburgh.
Hugh Millen replaced an injured John Elway and guided Denver on a 41-yard drive in overtime and Jason Elam kicked a 34-yard field goal with 3:48 remaining to give the Broncos (7-6) their fourth straight win and sixth in seven games.
The Chiefs (7-6) played without injured quarterback Joe Montana and lost for the fourth time in six games.
In a key NFC Central battle, Barry Sanders rushed for 188 yards and a touchdown and Dave Krieg threw two touchdown passes to lift the Detroit Lions to a wild 34-31 victory over the Green Bay Packers.
Sanders, who leads the league in rushing, moved his season total to 1,594 yards, breaking his own club record of 1,548 set in 1991. The Lions (7-6) improved their position in the race for an NFC wild card spot, while the Packers (6-7) lost their third in a row and had their playoff chances damaged.
The San Francisco 49ers remain a tie-breaker in front of Dallas for overall best record with a 50-14 drubbing of the Atlanta Falcons. Steve Young threw three touchdown passes and ran for two scores as the 49ers (11-2) notched their eighth straight win.
San Francisco, which set a league season-high for points, has the edge on Dallas as a result of its 21-14 win over the Cowboys on November 13th. Atlanta dropped to 6-7.
In other games today, Arizona blew past Houston, 30-12; New Orleans routed the Los Angeles Rams, 31-15; and Tampa Bay edged Washington, 26-21.
Week 14 began Thursday night as Minnesota Vikings beat the Chicago Bears, 33-27, in overtime in a key NFC Central Division game. Cris Carter caught a 65-yard touchdown from Warren Moon 5:46 into overtime to give the Vikings the victory and the lead in the NFC Central.
The Vikings (8-5) tied the Bears (8-5) for first place in the NFC Central. Minnesota holds the tiebreaker advantage as it has swept the season series from Chicago.