Kevin Durant and reserve Kevin Martin each scored 15 points for the Thunder, who never trailed after Durant converted a pair of free throws with 7:44 remaining in the first quarter.
Jonas Valanciunas led the Raptors (1-3) with 18 points and Andrea Bargnani had 16.
Casey said he "didn't recognize" his team Tuesday night.
"We knew they would come out aggressive, focused and we had to meet that type of intensity and we didn't," the coach said. "That was disappointing for our young team, but it was a learning experience."
Brooks was able to rest his starters in the fourth quarter as the Thunder improved to 2-2 with their highest-scoring game of the season. Brooks played 13 of the 14 players on his roster, and Oklahoma City had six players in double figures.
"You need nights like that in the NBA," Martin said. "You're not going to be able to beat teams with three guys, and tonight Serge stepped up and Eric (Maynor) played well. They're going to have nights like that and we're going to need them."
The Thunder shot 50 percent from the floor in the first half to lead 57-38 at the break and finished the game shooting 47 percent. Oklahoma City will play at Chicago on Thursday.
NOTES: The Thunder outrebounded Toronto 46-37, including 39-29 on the defensive end. ... Oklahoma City scored 42 points in the paint.