Brian Austin Green and Megan Fox
09/19/2012 AT 06:00 AM EDT
and Brian Austin Green
stepped out for lunch together on Thursday at Casa Vega in Los Angeles.
"They were very nice, and she looked very cute pregnant," an onlooker tells PEOPLE.
The parents-to-be enjoyed guacamole, taquitos, tortilla soup and cheese enchiladas.
Although the couple is expecting their first child together, the Transformers
star is already a stepmom to Green's 10-year-old son, Kassius Lijah.
– Jennifer Garcia