After his father died on New Year's Day 1969, Miller ran in a March 1969 special election to succeed him in California's 7th State Senate district, but Republican John A. Nejedly defeated him 57% to 42%.

[4] On April 10, 1975, Miller walked out of the House chamber during President Ford's State of the Union Address when he requested military aid for South Vietnam.

A review of Miller's career states that, although he has been unsuccessful in his pursuit of top party positions, he has "learned a legislator’s virtues of patience, timing, and creativity.

Miller has focused on pension issues, reinstating Davis-Bacon Act wage protections for Gulf Coast workers in the wake of Hurricane Katrina.

In addition, Miller has worked on education issues such as protesting student aid cuts,[14] increasing No Child Left Behind Act funding, and investigating the Bush administration's hiring of Armstrong Williams to promote that law.

[15] In 2007, as chairman of the House Education and Labor Committee, Miller sponsored the Fair Minimum Wage Act of 2007, which was enacted into law as an amendment to another bill.

Miller sponsored the Protecting Students from Sexual and Violent Predators Act, a bill that would require school districts receiving federal funds to give all employees criminal background checks.

[20] Miller has petitioned to clear the names of the sailors of the World War II Port Chicago disaster in which more than 200 black men were court-martialed and 50 convicted of mutiny for refusing to continue to load ammunition onto warships after a tremendous explosion killed hundreds.

"In 2024, Ana Cabrera of MSNBC remarked, "Congressman George Miller of California, who had confronted Trump in 1993...said that was the most irresponsible testimony he had heard in his 40 years in Congress.

"[26] Miller, a superdelegate in the Democratic Party's 2008 presidential primary, pledged his support to Barack Obama despite the fact that his district voted for Hillary Clinton.

Miller cited Obama's grassroots fundraising campaign, first-place win in the Iowa caucus and strong showing in the New Hampshire primary, leadership style and opposition to the Iraq War as reasons for his endorsement.

Miller describes her as the leader he has been waiting for 30 years and supported her when the Democrats lost the majority in 2010, saying that the Obama administration did not defend her or her accomplishments.

[12] Their friendship has spanned "over 30 years and many plane trips to Washington from their neighboring California districts," with some colleagues saying that they have become so close that they finish each other's sentences.

[30] Miller owned a townhouse in Capitol Hill, Washington, D.C. for decades, renting rooms to fellow members of the U.S. House, even after some moved to the Senate.