Devin Shore scored, and Mikko Koskinen made 26 saves for the Oilers (30-23-4), who have lost three in a row and six of their past eight games.
"I think if we start looking at the standings, that would not be the way to go," Shore said. "I think we're trying to build something as a group and the way we want to play, and I think that needs to be our focus and let results be a byproduct of that. A lot of games left. We're over the halfway mark, but I think if we start looking at the playoff picture, I don't think that's a recipe for success right now."
Toffoli put Calgary up 1-0 at 6:27 of the second period with a power-play goal. Matthew Tkachuk tried to pull the puck between his legs for a shot, but he didn't connect and Toffoli shot the loose puck past Koskinen's glove.
The goal came after Markstrom made a blocker save on Brad Malone from the slot at 2:37 off a cross-ice pass by Colton Sceviour.
Toffoli scored again to make it 2-0 at 9:54, skating in on his off wing before shooting a one-timer from the left circle.
"When you look at the goals he scores, too, it's not one position or the same goal," Markstrom said. "He's a goal-scorer, and it's nice to have him on our team."