Maggette and his fellow reserves outscored Atlanta's backups 35-6 in the first half and the Bucks continued their offensive awakening, beating the Hawks 108-91 on Wednesday night.
The Hawks began the season 6-0 before the three straight losses, including two at home. The lopsided loss to the Bucks stunned the Hawks.
"It's hard to explain," said Hawks center Al Horford. "I don't understand what happened."
The Bucks struggled with their offense early in the season and were last in the league in scoring with only 89.6 points per game before taking a 107-80 win over the New York Knicks on Tuesday night.
Maggette had 20 points and Brandon Jennings added 19 as the Bucks took back-to-back wins for the first time this season.
The Bucks trailed by 13 points in the opening period before taking a lopsided 33-14 advantage in the second period for a 54-40 lead at the break. The bench led the second-quarter surge.
"We've got to give our bench a lot of credit tonight," said Bucks coach Scott Skiles. "They came out and not only got us back in the game but, I believe, we had a 27-point turnaround in the first half."
The Bucks continued to stretch the lead after halftime. Jennings had back-to-back 3-pointers late in the third period to stretch the advantage to 30 points at 88-58.
"When adversity hit us in the face, we went our separate ways," said Atlanta's Josh Smith, who had eight points and eight rebounds. "We'll figure out what's going wrong, and we'll fix it really quick."
Skiles said the Bucks should receive a confidence boost from the win.
"Hey, look, if you come in here and are up  points over the Hawks, you're obviously doing something right out there," Skiles said.
Backup center Zaza Pachulia led the Hawks with 16. Horford had 14 points but only six rebounds as the Bucks took a 44-32 advantage on the boards.
Horford had 10 points in the first period as Atlanta's starters claimed a 20-7 lead. The advantage began to disappear when Hawks coach Larry Drew began substituting.
"Our starters have gotten us off to fast starts," Drew said. "I'm not getting the energy from the bench. ... That's the third game that's happened to us. I have to find better combinations to use that can sustain the energy."
The Hawks were stretched to seven games before beating the Bucks in the first round of the playoffs last season.
"This is a whole new season," said Milwaukee's Andrew Bogut, who had eight points. "People are going to build this rivalry up because they beat us in the playoffs, but it's pretty much a whole new team."
The Hawks couldn't match the Bucks' intensity, especially in the second and third periods, when Milwaukee outscored Atlanta 67-33.
Drew said his players were too easily frustrated.
"When it gets a little tough, we have a tendency to hold our heads down," Drew said. "I don't want to see our guys hang their heads."
Bucks forward Carlos Delfino missed his second straight game with a neck strain. ... Hawks forwards Marvin Williams (bone bruise in his right knee) and Maurice Evans (sore right knee) were held out after working out Wednesday morning. Williams has missed four straight games, and the Hawks are 1-3 without the starter. ... Bibby passed 14,000 career points with his first basket.