The couple was spotted shopping at Target together in Los Angeles with Simpson's four-year-old son Bronx on Thursday, Oct. 17.
Simpson, 29, was sporting her signature boho chic style, rocking studded black ankle boots, a blue silk kimono-style jacket and wide-brimmed black hat.
Her 24-year-old man also looked casual in a green shirt, black pants and boots while pushing the couple's jam-packed shopping cart around the store as Ashlee kept a watchful eye on her son.
Simpson and Ross, who were first romantically linked in early July, appear to be going stronger than ever.
Earlier this week, the blond beauty came out to support her man for his CrazySexyCool: The TLC Story premiere at the AMC Loews Lincoln Square in NYC, where Pete Wentz's former missus even sat with Evan's famous mom, Diana Ross.
Simpson has also reportedly been spending time in Atlanta while her boyfriend films the third installment of the Hunger Games series, Mockingjay: Part 1.