Buchanan was on her way to winning her third two-year term to represent the 16th Assembly District against challenger Republican Al Phillips, with 58 percent of the vote.
"I just want to say I'm thankful with the results and honored to represent the people in the Valley for two more years," Buchanan said.
She and Assemblyman Susan Bonilla addressed the crowd with Bonilla first speaking and saying that she had been fortunate to be unopposed.
"I've always had opponents," Buchanan said, citing her runs for the San Ramon Valley Unified School District board, where she served 18 years, and her last two runs for the Assembly.
"I'm excited about my new district," she continued, which runs from Livermore to Pleasanton, Dublin and north along the I-680 corridor and west to include Lamorinda. Her former 15th District included parts of Sacramento and San Joaquin counties.
Buchanan was hopeful that Proposition 30, Gov. Brown's proposal to fund education, would pass.
"If Prop 30 wins, then our schools win, which is as important as all of us winning," she said.
Then she led the crowd in the chant, "Four more years! Four more years!"
Bchanan's main campaign points were budget reform, jobs and the economy, and protecting education. She also ran on her support for legislative actions to create jobs.
"It must be our top priority," she said on her reelection website.
Buchanan, who lives in Alamo, has parted with her Democratic party on some business issues and has backed changes in public pensions opposed by organized labor.
"I do not have a predetermined agenda," she said.