Baltimore spotted New York a 5-0 lead in the first, but then came roaring back in the next frame to grab control of the contest -- all with two outs.
Mark Reynolds followed with a run-scoring ground-rule double and Omar Quintanilla next delivered a two-run single, cutting the deficit to 5-3.
Nick Markakis singled to load the bases and Young then stroked his first career grand slam, capping the big rally.
Markakis and Betemit combined to go 6-for-9 with four RBI for the O's, who clinched their three-game set against the American League East-leading Yankees.
Chris Tillman (4-1) collected the victory, yielding five runs (four earned) on eight hits with no walks and three strikeouts.
Nova ended up surrendering nine runs on 10 hits over five full frames.
Robinson Cano cracked a two-run homer during New York's five-run first.