The best-of-seven series now shifts to Chicago for Games three and four on Thursday and Sunday with the Bulls looking to avoid the sweep.
The Los Angeles Clippers, back in the playoffs for the first time in nine years, also took charge of their quarter-final easing past the Denver Nuggets 98-87 to head to Colorado up 2-0.
As usual, the Heat's two all-stars O'Neal and Dwyane Wade headlined the Miami effort but the supporting cast also made a big contribution.
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Jason Williams added 22 points to the win while Antoine Walker, stepping in for suspended Udonis Haslem, chipped in with 17 points and 10 rebounds.
"We had six guys in double figures but we didn't finish again and that disturbs me," Riley told reporters. "And it should disturb our players that we put ourselves in jeopardy after working so hard and playing so well. It happened the other night as well.
"But we're ahead 2-0 and that's what it's about."
Wade made his usual sizeable contribution with 21 points, seven assists, five rebounds and four steals that included some strong play at both ends of the court in the closing minutes.
The Heat appeared to have the game well in control opening up a 20-point third quarter lead but once again, the Bulls threw a scare into the Miami crowd as they rallied to trim the deficit to 108-104 with 1:15 to play.
But that would be as close as the Bulls would get, Wade blunting the comeback with clutch jump shot.
"We came out and respected the hell out of them," said Riley, back on the Miami bench following the death of his mother on Friday. "They present a lot of problems."
"That team's never going to stop coming. We found that out in Game one and found it out again tonight."
"We scored 115 tonight, 111 the other night. Offense I don't think is going to be a problem for us, it's sustaining the defensive intensity and mentality that we have to continue to work on."
In Los Angeles, Cuttino Mobley bagged 21 points and Elton Brand added 19 points and 11 rebounds sparking the Clippers to a 98-87 win over the Nuggets.
Sam Cassells added a double-double with 13 points and 11 assists but the 13-year veteran's most valuable contribution to the young Clippers continues to be his experience and leadership as Los Angeles heads to Denver for Thursday and Sunday's games three and four.
"We played solid man, played solid on defence and we win the game just like that," said Cassells, who owns two NBA championship rings. "This team hasn't accomplished anything. We were suppose to win at home and we won at home so the big chance for us is going to Denver."
After a holding on to claim a two point victory in Game one, the Clippers took control early bolting to a 25 point lead in the second quarter and from there were never threatened.
Marcus Camby paced the 16 points and 14 rebounds while Carmelo Anthony ran into early foul and was never a factor also hitting 16 points.
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