The left-hander, who started the season in the bullpen, pitched six sharp innings Tuesday in his third start of the year as Chicago claimed a 4-0 victory over the San Diego Padres.
Montgomery (1-3) allowed three hits, walked two and struck out four as the Cubs (36-34) won their third straight.
"I felt strong, even toward the end, was able to get quick outs and being efficient helps in that as well," said Montgomery, who threw 75 pitches on the night. "I think this last time in between (starts) having an extra day, really gave me a chance to get my legs under me a little more."
Anthony Rizzo's leadoff homer provided the only run needed while Montgomery set the tone from the start, retiring the first seven Padres batters and relied on the Cubs defense' to snuff out other Padres' threats.
"When you're able to pitch like that, you give your team a chance to get into the flow of the game," Cubs manager Joe Maddon said. "We caught the ball really well. We made nice plays. And Anthony (Rizzo) did it again, jump starting the offense."
Right hander Jhoulys Chacin (6-6) also worked six innings and saw a personal two-game winning streak snapped as the Padres (28-44) dropped their third straight. Chacin gave up two runs on five hits, walked three, struck out six and hit two batters.
The Cubs tried to add insurance runs in the sixth, loading the bases with one out. But Chacin worked out of the threat, including an inning-ending ground out to second by pinch hitter Tommy La Stella.
"(Chacin) was great," Padres manager Andy Green said. "You get past that first batter of the game -- obviously he missed a spot to Rizzo pretty badly there and made him pay -- but after that I thought he battled really well. Made big pitches when he had to."
San Diego threatened in the seventh with two runners on and two outs, but reliever Carl Edwards Jr. struck out pinch hitter Matt Szczur to end the inning. Cubs reliever Pedro Strop escaped a similar jam in the eighth.
The Cubs added two runs in the eighth as Ian Happ's solo homer -- his ninth of the season -- led things off. Javier Baez singled to deep center, advanced to third on Franchy Cordero's error and scored as pinch-hitter Albert Almora doubled to center.
Justin Grimm worked a one-two-three scoreless ninth.
Rizzo homered to center in his opening at-bat for a 1-0 Cubs lead. It was the third time in seven games he clubbed a home run from the lead-off spot. It was his team-leading 17th homer of the season and the 150th of his Cubs career.
Rizzo learned before the game that he will not be fined or suspended in the wake of a Monday home plate collision with Padres catcher Austin Hedges. There was no apparent San Diego retaliation for the incident.
Hedges sat out Tuesday after suffering a thigh bruise but could return to action as soon as Wednesday.
NOTES: Monday's leadoff home run by OF Jose Pirela was the Padres' sixth of the season, first in the NL and tied for second in the big leagues. ... Padres 2B Yangervis Solarte was in Tuesday's starting lineup but never took the field after suffering a strained left oblique and was replaced by Chase d'Arnaud. Manager Andy Green said Solarte might be bound for the disabled list. ... The Padres send RHP Miguel Diaz (1-1, 7.36 ERA) out for his third career start Wednesday, facing Cubs RHP Eddie Butler (3-2, 4.41). ... Cubs OF Jon Jay continued to rank among leading NL pinch hitters, third with a .385 average. ... Chicago's brief three-game homestand this week interrupts a stretch of 17 of 20 games on the road through July 2. ... Cubs 3B Kris Bryant holds a substantial 300,000-vote lead for starting NL All-Star third baseman in the latest voting, but teammate Anthony Rizzo still trails the Nationals' Ryan Zimmerman by more than 150,000 votes for the first base starting nod.