Johnson, who was 5-for-8 from 3-point territory, had 15 in the first half for the Rams (20-5, 8-2 Atlantic 10) as they avenged a 10-point loss on the Colonials' home court a month ago.
Isaiah Armwood and Maurice Creek had 17 points each and Patricio Garino had 16 for George Washington (19-5, 7-3). The Colonials played without No. 2 scorer Kethan Savage (13.4 ppg) because of a broken left foot. They played the last 43.2 seconds without coach Mike Lonergan, ejected after his second technical.
The Rams seemed to have the game in hand, but after George Washington missed its first nine 3-point attempts, the Colonials made their next five. The last of the five, by Creek with 9:13 to play, pulled them within 59-54, quieting the 48th consecutive sellout crowd, which filled the Siegel Center despite a snowstorm that started long before the opening tip.
Johnson woke them 13 seconds later with his fourth 3-pointer of the game, and after Garino made a free throw, the Rams reeled of 10 points in 1:17, getting 3s from Brandenberg and Johnson, to go up 72-57.
George Washington trailed 73-57 before the Colonials' 9-1 burst got it back to 74-66, but they got no closer and the Rams answered every basket, including their 13th and final 3-pointer from Brandenberg.
Trailing 10-7, the Rams went on an 18-2 surge started by Johnson's second 3-pointer. He had seven in the spree and Graham had six, including a four-point play to close it, making it 25-12.
The Colonials fell behind by as many as 21, at 39-18, then scored 10 of the next 11 points to close the gap to 12 before a three-point play by Reddic and Johnson's floater made it 45-28 at the half.
Follow Hank on twitter at: http://twitter.com/hankkurzjr