Roger Espinoza and Opara were on the score sheet as Sporting claimed a 2-1 win against the LA Galaxy on Saturday.
Espinoza struck from distance in the 22nd minute, Galaxy goalkeeper Clement Diop punching the effort into his own net.
Then came Opara's brilliant goal as the center back delivered with a bicycle kick to put his team 2-0 up.
David Romney pulled a goal back in the second half for the Galaxy, but Sporting held on to move five points clear atop the conference.
Accam netted three times as Chicago thrashed Orlando City 4-0.
The Ghanaian opened the scoring in style just three minutes in, his sublime back-heel from a Matt Polster cross beating goalkeeper Joe Bendik.
Accam made it 2-0 just five minutes later, getting on the end of a Bastian Schweinsteiger pass before rounding Bendik and finishing.
MLS top goal scorer Nemanja Nikolic struck early in the second half on a ball from Accam before the Ghanaian completed his hat trick, and the resounding win, from the penalty spot.
David Accam was on another level tonight. pic.twitter.com/kFhYWtBC9f— Major League Soccer (@MLS) June 25, 2017
New York City claimed derby bragging rights with a 2-0 win over the Red Bulls thanks to goals from Jack Harrison and Ben Sweat.
Just four minutes earlier, United's Lamar Neagle was denied from the penalty spot as the home side claimed the win.