The Royals were, for the most part, clinical in front of goal as Hal Robson-Kanu opened the scoring before Harte and Long stole the show to seal a deserved win, despite Leroy Lita netting a brace of his own in two rare Boro attacks.
Robson-Kanu opened the scoring from Jimmy Kebe's cross and although Lita pegged his former side back, Harte netted his first of the afternoon with a sublime free-kick shortly before half-time.
The full-back received a slice of luck for his second goal when another free-kick went across the face of goal and into the net.
Harte then set up Long with a pinpoint cross to leave the striker with the simplest of finishes before the 24-year-old sealed victory after bursting through on goal and sliding home.
Lita pulled one back from the penalty spot after Matt Mills fouled the striker in the area but it proved mere consolation.
The hosts were looking to build on their FA Cup victory over Everton in midweek and their bright start was rewarded when Robson-Kanu, who replaced Jobi McAnuff in the only change to the Royals starting line-up, broke the deadlock in the 14th minute.
Kebe's early right-wing cross was met by an unmarked Robson-Kanu at the far post and the winger powered a downward header past Jason Steele.
If the Boro goalkeeper was at fault for the goal, he made up for it moments later to keep the deficit to just one goal after he somehow managed to tip Noel Hunt's close-range volley round the post.
It proved to be a crucial save as, against the run of play, former Reading striker Lita hauled Middlesbrough level in the 29th minute.
The ball was cleared to Andrew Taylor on the edge of the area and, although Alex McCarthy did well to keep out the initial effort, Lita, who spent four years at the Madjeski Stadium, followed up to drill home.
Their joy was short-lived, though, as after Nicky Bailey had made a rash challenge on Long, Ian Harte curled a magnificent 25-yard free-kick past Steele six minutes later.
It was no less than Brian McDermott's men deserved but their opponents had clearly not learned their lesson when Taylor fouled Brynjar Gunnarsson on the right three minute after the interval.
Harte's whipped free-kick eluded everyone in the area before sailing past substitute Boro keeper Connor Ripley and into the net at the far post.
Boro were reeling and Long looked to have ended the game as a contest in the 54th minute when he headed home from the impressive Harte's deep cross on the left.
Kebe spurned a glorious chance when he shot wide after rounding Steele but Long showed the midfielder how it was done when he latched on to Jay Tabb's through-ball before racing through on goal and striking past an uncertain Ripley in the 68th minute.
Lita got his second of the afternoon from the penalty spot after Mills had fouled the striker in the area three minutes later, but it was too little too late.