Osaka, the third seed, faced a tricky contest against the Frenchwoman, who was ranked a career-high of fourth in late 2018, but never gave her a sniff in the 6-2, 6-3 victory in 61 minutes.
The three-time Slam winner, however, had an uneasy feeling Wednesday, waking up in a panic after a nightmare.
“Last night I had a dream that I lost this match, and I really didn’t feel good about it,” she said.
“My dreams are very telling of the future.
“Going into this match I was really nervous. So then I just talked to my team, and I felt better about the situation.”
The 2019 Australian Open champion cruised through the opening set and then snuffed out any challenge from 43-ranked Garcia with a break in the sixth game of the second, before finishing it off in style with her 10th ace.
“It’s really hard to play a player like her, because I never know when she’s going to swing for the ball or anything,” she said.
“I knew that she was going to be aggressive on my second serve, so I felt like I had to do better there.
“I just have to keep staying steady. Happy that I was able to do it in two.”
She next faces 27th seed Ons Jabeur of Tunisia, a quarter-finalist at last year’s Australian Open whose talent has long impressed Osaka.
“I always felt like watching her. She’s a player that can do anything, and I always felt like she should be where she is now and even higher,” she said of the 26-year-old.
Osaka, now unbeaten in 16 matches over the past 12 months, including the US Open final, is eyeing redemption after her title defence last year ended with a shock loss to American teenager Coco Gauff in the third round.