The suspects - a 31-year-old man and a 29-year-old woman - scaled fences at Windsor’s Royal Lodge on April 25, where they were arrested, the Sun reports.
The couple broke in close to where the 95-year-old monarch goes for walks with her corgis and rides horses.
It is also near All Saints Chapel where the Queen attends Sunday service and Prince Andrew’s home.
Andrew was understood to have been home during the latest incident.
Following the arrest, the two suspects were taken to Maidenhead police station, where they were later released on bail pending further inquiries.
Princess Diana’s former personal protection officer called the estate’s security a "farce", saying it made the Queen "vulnerable".
It comes just days after a woman was allegedly allowed into the grounds of Prince Andrew’s home by mistake.
She entered the Royal Lodge while Andrew, was home, and was stopped by a member of staff.
The woman was arrested on suspicion of burglary and was later sectioned under the Mental Health Act after pretending to be Andrew’s fiancee and claiming she was meeting him for a lunch date.
A source told the newspaper: “This is an astonishing lapse. Everyone was on high alert after the first intruder, now this happens. Heads could roll. It is unforgivable.
“The couple wandered around for ages before anyone spotted them and police were called.”
The Met provides full-time, armed security to senior royals at their palaces and homes.
The Queen is also guarded by the Foot Guards of the Household Division based at Victoria Barracks, just outside the castle walls.
The Queen has been away from Buckingham Palace for over a year and has been shielding at Windsor Castle for seven months.
She is joined by about 20 members of staff in what has been called the HMS Bubble.
Thames Valley Police have been approached for comment.