"We needed the win," Beal said. "It was just plain and simple. We were going to do whatever it took to get the win."
Wade almost provided his own heroics, missing a game-tying jumper in the lane with 4.1 seconds remaining after converting a three-point play to force overtime.
The loss dropped Miami into eighth, a half-game behind seventh-place Milwaukee.
Now 36, Wade continues to look reinvigorated since returning to Miami in a trade from Cleveland last month. The 12-time All-Star and three-time NBA champion has scored 20 or more points in three of the Heat's last five games, and Tuesday was their go-to guard down the stretch.
"Everything goes out the window at the end of games," Wade said. "It's like a mechanism where you just lock in."
Tomas Satoransky added 19 points and Markieff Morris had 16 points and 13 rebounds for Washington. Morris' baseline 3-pointer off Beal's feed made it 113-109 with 1:06 left in overtime.
Wade brought Miami within one with 12.9 seconds remaining after he lured Kelly Oubre into a foul on a 3-point attempt, then sank three free throws to make it 114-113.
After Satoransky hit one of two foul shots, Wade got free in the lane but missed a floater following a pump fake. Kelly Olynyk's follow also missed. Oubre hit a pair of free throws to seal it.
"I was a little nervous with the D-Wade floater because it was a good move," Beal said. "That was definitely a great look for him."
Miami led only once, but stayed close throughout the second half. Wade tied it for the third time with 22 seconds left in regulation, driving by Morris, absorbing Beal's foul, hitting a leaning layup and then converting a three-point play to make it 105-all.
TIP-INS
Heat: G Wayne Ellington (thigh bruise) was out for a fourth consecutive game but worked out pregame. "We're going to push him in this workout a little bit more and see how he responds tomorrow," Heat coach Erik Spoelstra said. ... Wade scored in double digits in the second game of a back-to-back set for the first time since his Miami return.
Wizards: F Otto Porter left the game with 8:29 remaining in regulation with a bruised hip after colliding with Wade trying to reach a loose ball. ... Morris' double-double was his first since Feb. 5.
TYLER TOO
Miami's Tyler Johnson scored 21 points and played more than 38 minutes in his second game back from a thigh bruise.
"It was great to see him out there being aggressive and playing with confidence," Spoelstra said. "He certainly played at least 20 more minutes than I anticipated playing him."
WALL'S PROGRESS
Wizards coach Scott Brooks said Wall worked out on Monday afternoon.
"He actually moved around more than light shooting," Brooks said. "Moved around pretty good. Not a lot of reps, but got a good sweat, a good workout. That's another step in the progress of his return."
QUOTABLE
"There's something so special and different when Dwyane Wade puts on that Miami Heat jersey. It transcends sport. And the impact reverberates all throughout South Florida. There's only a few players who have that type of impact." - Spoelstra. Wade is back in Miami after spending his first 13 NBA seasons with the Heat.
UP NEXT
Heat: Face Philadelphia at home on Thursday.
Wizards: Visit New Orleans on Friday.