On a bright June afternoon in the San Fernando Valley, the summer’s unlikeliest action hero sits down at a small dining table in the tidy ground-floor apartment that she shares with two cats. Offering her guest a plate of cookies, June Squibb explains that she previously lived for two decades in a different apartment on the second floor, but three years ago her son Harry insisted she move down to this unit so she wouldn’t have to navigate stairs every day. “He was right — moving down here was the best thing I could have done,” she says.

This may not seem like the typical setting for an interview with an action star. But then again, Squibb is 94 years old and nothing about her career has been typical. After decades on the stage in New York, she made the leap to film and TV when she was already in her 60s and quickly found herself working for directors like Woody Allen, Martin Scorsese and Alexander Payne.

When she was 84, Squibb earned a supporting actress Oscar nod for her turn in Payne’s 2013 film “Nebraska,” and now, at an age when many actors have long since retired or died, she is finally stepping into the spotlight with her first starring role. In the comedy “Thelma” (in theaters Friday), Squibb plays a strong-willed grandmother who is duped out of $10,000 by a phone scammer and embarks on a quest to get back what is hers, taking to the streets on a scooter hijacked from an elderly friend, played by “Shaft” star Richard Roundtree . (The actor died.