For months, now, whenever actor Jay O. Sanders would get a break on a movie or television set, he’d hie himself to his canvas chair, pull out a well-thumbed copy of Macbeth, and peruse the text. He’d wanted to play the murderous thane for years, and this year, on his 50th birthday, he decided the present he wanted most was " permission to pursue this role without worrying about where I would do it. "

The actor is speaking over the phone between rehearsals for the al fresco production of the Scottish play that will be the eighth annual offering of free Shakespeare on Boston Common by Commonwealth Shakespeare Company, beginning next Friday. (Last summer’s Henry V drew nearly 50,000 people during the course of its run.) This spring, Sanders spent months " reading, thinking, and looking at art related to it. People would see me reading the play and say, ‘Oh, are you doing this?’, and I’d say, ‘Ya-ah,’ and they’d say, ‘Where?’  " Sanders pauses and chuckles briefly. " I’ve been pursuing this like a crazy person, and I mentioned it to my agents. Then I got a call saying Steven Maler wanted to do it. I told him, ‘I have my own concept about this, but the greatest gift in the world would be to focus on the role one time through.’  "

Maler’s production has a Central American theme. " A starting point for me about the production was looking at situations in Central and South America, where the political and the military have collapsed into one regime, " says the CSC director. " There are many examples of this, like the Ceausescus and the situation in North Korea, where there’s a deification of the leader. " Sanders declines to share his vision of the play in so brief an interview but explains that filming The Day After Tomorrow (to be released next year) in Vancouver put him in touch with " the sensibility of the Inuit nation, which was very much in tune with the world I was imagining. Yet much to Steven’s credit, I have felt completely at home and free to collaborate with him and use all the knowledge I have about the play without pitting my vision against his. I’m completely in the world that he has imagined. "

Although Sanders does a lot of theater work, including a 1999 turn as Petruchio opposite The West Wing’s Allison Janney in the New York Shakespeare Festival’s Central Park The Taming of the Shrew, he’s also had frequent featured roles in films and evening TV dramas like Law & Order. " Jay is sort of like John C. Riley, who all of a sudden happened to be in the right three films at the right moment, which pushed him through the surface, " says Maler. " What I adore about him is that he’s worked in everything from small Off Broadway plays to The Exonerated to Shakespeare in Central Park to major films. We had a pretty extensive list when we first started casting, and he was at the top of the list. "

One attribute that Sanders brings to the role is size. " Jay is a huge man, " says Maler. " He’s like six-foot-four with a big voice, and it’s interesting to see this big man who has this ‘Everyman’ look who has this capacity to look inside himself with such scrupulousness and brutality. "

Sanders displays a refreshing frankness about his own gifts and abilities. " This part suits me particularly well. I’ve seen a lot of smaller men in the role who put a lot of energy into showing how strong they are and how fierce they are. I don’t have that problem — I don’t have to prove myself. "

Maler concurs. " What we hear at the start of the play is that he cut a man in half — he took this battle that’s going radically against them and single-handedly turns this battle. You have to have the sense that this man is a force on the battlefield and that he has a madness, frankly, that’s awe-inspiring. "

Playing the warrior is one thing, but the other side of Macbeth — the tortured husband and usurper — also presents a challenge. " Macbeth sees what’s coming and goes there but fights it in himself, which is actually no different from Hamlet, " says Sanders. " It’s about finding your resolve for what you think must be done, but as you’re doing it, you’re questioning yourself every step along the way. " And he couldn’t be happier spending every waking hour walking and talking Macbeth: " I am the proverbial pig in that which he loves to roll in. "

Macbeth will be presented by Commonwealth Shakespeare Company at the Parkman Bandstand on Boston Common July 18 through August 10. All performances are free and open to the public. There is an American Sign Language-interpreted performance next Saturday, July 19. For more information (including weather cancellations), call (617) 532-1212 or visit commonwealthshakespeare.org