In 1942, Carpenter began covering the White House and Congress for the Austin American-Statesman. For the next eighteen years, she reported on presidents from Franklin D. Roosevelt to John F. Kennedy as a Washington reporter.

Les and Liz Carpenter were married in 1944, after he was discharged from the United States Navy during World War II. They launched the Carpenter News Bureau in the National Press Building in Washington, D.C. For the next sixteen years Carpenter covered Congress and the White House for various newspapers in Texas. She missed work only briefly when their two children, Scott and Christy, were born.

She was still a working reporter at the time of the 1960 Democratic National Convention in Los Angeles, California. She soon joined the staff of Lyndon B. Johnson in his campaign for Vice President in 1960 and traveled on his foreign missions as a press spokeswoman. After Kennedy's election, she became the first woman executive assistant to the vice-president.

Carpenter was in Dallas on November 22, 1963, at the time of the assassination of John F. Kennedy. She drafted the fifty-eight words that Johnson used on his return to Washington:

This is a sad time for all people. We have suffered a loss that cannot be weighed. For me, it is a deep personal tragedy. I know that the world shares the sorrow that Mrs. Kennedy and her family bear. I will do my best. That is all I can do. I ask for your help and God's.

Following Johnson's succession to the presidency, Carpenter became the first professional newswoman to be press secretary to a first lady for Lady Bird Johnson (1963–1969), for whom she also served as staff director. Carpenter also contributed to the speeches of President Johnson, particularly in the field of humor by creating the White House Humor Group.

After the Johnson Administration ended in 1969, she wrote Ruffles and Flourishes, her account of her White House experiences.

She was a vice president of Hill and Knowlton in Washington after leaving the White House. In 1971, she was one of the founders of the National Women's Political Caucus and co-chair of ERAmerica, traveling the country to push for passage of the Equal Rights Amendment.

She was appointed by President Gerald Ford to the International Women's Year Commission, by President Jimmy Carter to serve as Assistant Secretary of Education for Public Affairs, and by President Bill Clinton to serve on the White House Conference on Aging.

In 1974, Les Carpenter died suddenly of a heart attack at the age of fifty-two, just a year after the death of Lyndon Johnson. In 1976, Carpenter returned to Austin: "Family roots, the love for Texas and the University of Texas and the LBJ Library brought me back home." She purchased a house, which she named "Grass Roots", located in the West Lake Hills overlooking the Austin skyline and the Colorado River

Her books include: Unplanned Parenthood, Random House 1994; Getting Better All the Time, Simon and Schuster 1986, as well as countless articles and forays on the lecture circuit. Start With a Laugh, gives humorous advice on speech writing, was published by Eakin Press and launched at the opening of the National Women's Museum: An Institute for the Future in Dallas. Her most recent book, Presidential Humor[1], Bright Sky Press 2006, is a compilation of quips and quotes from "George the First to George the Worst."

Carpenter was named a Distinguished Alumna of the University of Texas in 1975, and in 1990 was named distinguished alumnae of the Department of Communications. She was named by Governor Mark White to the Texas Women's Hall of Fame. She was given the ProBene Award of the College of Liberal Arts.

The Liz Carpenter Lectureship was established in 1984 by a group of her friends, including Erma Bombeck and Mark Russell, who gave a performance at the Paramount Theater to raise funds for it.In the last several years, Mrs. Carpenter's lectureship in the College of Liberal Arts has brought President Bill Clinton, President Gerald Ford, Hillary Rodham Clinton, Jehan Sadat, Maya Angelou, Bill Moyers, Jane Goodall, and writers such as Betty Friedan, Nora Ephron, Shana Alexander, and Jean Auel and nationally known humorists such as Fannie Flagg and Carol Channing.

The Liz Carpenter Award is given annually for the best scholarly book on the history of women and Texas published during the calendar year. The Award was established in 1992 by an anonymous donor who is committed to the publication of scholarly research on the history of women and Texas. The award honors Liz Carpenter, a sixth-generation Texan, for her commitment to the pursuit of the history of women in Texas and for a lifetime of achievements that qualify her as a maker of that history.

She is the recipient of Alpha Phi's Frances E. Willard Award in 1980. She died in Austin, Texas in March 2010.

"Liz Carpenter is much more than an American original: she is an American and a Texas original. Her inside stories of our nation's political life over the last half-century are priceless." —Walter Cronkite

"No one remains the same person after meeting Liz ...(she) makes Auntie Mame look like a shut-in." —Erma Bombeck

"Her combination of wit and wisdom is infectious, encouraging, enlightening. Texas never had a truer daughter. Her zest for life is an example to us all." —James Michener

"(Liz is) the tilt-a-whirl at the State Fair with all the lights on and the music. The only difference between Liz and a tilt-a-whirl is that, with Liz, the ride never comes to an end." —Ann Richards

"...a human dynamo, P.T. Barnum. She could sell anyone the proverbial Brooklyn Bridge or the Washington Monument." —Helen Thomas

"She manages to phrase issues the way people experience them, rather than using all those words that end in t-i-o-n and deaden your brain." —Gloria Steinem