Oates will handle the forwards and Stevens will oversee the defense, Lamoriello said at a news conference before Saturday's morning skate.
"I'll go on the bench to make sure it works for now," Lamoriello said.
There will be no official head coach for the rest of the season. Lamoriello plans to remain on the bench "until I feel comfortable with the situation."
In another Group B game, Nashville draft pick Kevin Fiala scored twice in Switzerland's opening 5-2 victory over the Czech Republic.
In Group A in Montreal, Slovakia beat defending champion Finland, 2-1; and Canada played Germany.