[3][5] He operates a successful agricultural business known as Miller Nursery where he grows trees, shrubs and decorative plants near Stephenville, Texas.

[6][7] The bill would have repealed a 1949 state law that prohibits the sale or transport in Texas of horsemeat intended for human consumption.

[7] In 2011, Miller authored legislation (dubbed the "Pork Chopper Bill") that allowed licensed hunters to contract with landowners to shoot feral hogs and coyotes on their property via helicopter.

[8] The conservative Miller was unseated in the Republican runoff election held on July 31, 2012, by osteopathic physician J. D. Sheffield of Gatesville in Coryell County.

[18] In June 2017, the Commission resolved two of the complaints, sanctioning Miller for improper accounting in reporting political contributions and expenditures and fined him $2,750.

[22] Miller considered challenging Governor Greg Abbott in the Republican primary in 2022, but in June 2021 he announced he would seek re-election to a third term as Ag Commissioner.

In his first official action as commissioner, Miller granted full amnesty to cupcakes at a press conference on January 12, 2015, in which he drew attention to a previous repeal of a ban on junk food in Texas schools.

[31][32] In February 2015, Miller took a trip to compete in the Dixie National Rodeo in Jackson, Mississippi using Texas state funds.

[33] Miller's office initially defended the use of state funds, explaining that the commissioner intended to meet with Mississippi agriculture officials.

[34] In December 2018, the Texas Ethics Commission fined Miller $500 for the trip; a report released by the commission stated "No meetings besides the horse show appear on any official Texas Agriculture Department schedules," and that Miller "has not adequately explained why he initially reimbursed the state with political funds before reimbursing his political account with personal funds.

"[35] Six months after taking office, Miller reversed a ban, instituted in 2004 by then-Agriculture Commissioner Susan Combs, on soft drinks and fried foods in public schools.

Miller called the proposed increase "essential money" to keep his department operating and blamed legislative cuts for the need for the higher fees.

Representative John Otto of Dayton, the chairman of the House Appropriations Committee, said that fee hikes could result in lost revenue to the department because farmers and ranchers may choose alternative services.

The inspection initiative was designed to fight the illegal practice of capturing (or skimming) credit card information from gas pumps.

A judge in Austin halted Miller's proposal after Wild Boar Meats, a North Texas hog processor, sued on grounds that the poison may have unintended consequences.

[58] In April 2023, amid a wider push by the Texas state government to adopt policies targeting transgender people, Miller issued a "dress code and grooming policy" that ordered Texas Department of Agriculture employees, interns, and contractors to dress "in a manner consistent with their biological gender" and said that employees could be disciplined, including terminated, for failing to do so.

[59][60] Attorneys for the ACLU of Texas said that the rules violated Title VII (which prohibits employment discrimination), the First Amendment, and the Equal Protection Clause.

In July of 2024, Miller kicked off a bus tour, routing through battleground states across the country, in support of Donald Trump's bid for a second term in the White House.

[68] In August 2015, Miller posted a cartoon on his Facebook page that suggested the United States should launch a nuclear attack on the Middle East.

Miller received harsh criticism for the post and eventually removed it, but he termed the cartoon "thought provoking" and vowed not to apologize for his action.

[75] In May 2019, Miller received backlash from Muslim groups after posts on Facebook and Twitter called for Austin Mayor Steve Adler to not attend a Ramadan event headlined by Rep. Ilhan Omar.

[76] Miller tweeted "I am shocked to learn that Austin's Jewish Mayor Steve Adler plans to share the stage at an upcoming Ramadan dinner with controversial Minnesota Rep. Ilhan Omar.

[77] Miller followed up with a Facebook post classifying Omar's remarks as "hate speech" and saying that "repeated attacks upon the Jewish State of Israel have no place in a city like Austin that prides itself on diversity and inclusiveness.

"[82] In 2017, Miller posted on his campaign's Facebook page a story about two Texas hunters supposedly attacked while camping by Mexican illegal immigrants.

The suit, which plaintiffs aimed to make into a class action, was sponsored by America First Legal, a group founded by former Trump administration officials, most notably former senior advisor Stephen Miller.